lukart

The ASRock Z390 Taichi is very solid and it can often be found for a little less than $200. Board has good enough VRMs for a decent overclock on a 9900K if your case has decent airflow.

It's one of the cheapest RAM and it is 3000MHz, but ok:
PCPartPicker part list / Price breakdown by merchant
CPU: AMD - Ryzen 3 2200G 3.5 GHz Quad-Core Processor  ($134.00 @ Mike's Computer Shop) 
Motherboard: ASRock - B450M PRO4 Micro ATX AM4 Motherboard  ($77.63 @ Vuugo) 
Memory: Team - Vulcan 8 GB (2 x 4 GB) DDR4-3000 Memory  ($84.99 @ Newegg Canada) 
Storage: Kingston - A400 120 GB 2.5" Solid State Drive  ($29.70 @ Vuugo) 
Case: Corsair - 200R ATX Mid Tower Case  ($68.99 @ Powertop) 
Power Supply: Corsair - CX (2017) 550 W 80+ Bronze Certified ATX Power Supply  ($64.99 @ Amazon Canada) 
Total: $460.30
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-01-16 16:13 EST-0500

PCPartPicker part list / Price breakdown by merchant Type Item Price CPU AMD - Ryzen 3 2200G 3.5 GHz Quad-Core Processor $153.00 @ Shopping Express Thermal Compound Cooler Master - HTK-002 0.01 g Thermal Paste $3.00 @ Umart Motherboard ASRock - B450M PRO4 Micro ATX AM4 Motherboard $129.00 @ Scorptec Memory Kingston - FURY 8 GB (2 x 4 GB) DDR4-2666 Memory $92.18 @ Amazon Australia Storage Kingston - A400 240 GB 2.5" Solid State Drive $49.00 @ Shopping Express Storage Western Digital - Caviar Blue 1 TB 3.5" 7200RPM Internal Hard Drive $54.50 @ Shopping Express Video Card Gigabyte - GeForce GTX 1050 2 GB OC Low Profile Video Card $179.00 @ Shopping Express Case Thermaltake - Versa H18 Tempered Glass MicroATX Mini Tower Case   Power Supply Corsair - CXM 550 W 80+ Bronze Certified Semi-Modular ATX Power Supply $99.00 @ Shopping Express Wireless Network Adapter TP-Link - TL-WN881ND PCI-Express x1 802.11b/g/n Wi-Fi Adapter $15.00 @ Umart Other Phanteks Halos 120mm RGB LED Fan Frame $15.00   Prices include shipping, taxes, rebates, and discounts     Total $788.68   Generated by PCPartPicker 2019-01-17 09:39 AEDT+1100    plz tell

Some changes, better CPU, better PSU and mobo..
 
PCPartPicker part list: https://pcpartpicker.com/list/jn8tyX
Price breakdown by merchant: https://pcpartpicker.com/list/jn8tyX/by_merchant/
CPU: AMD - Ryzen 7 1700 3 GHz 8-Core Processor  ($169.89 @ OutletPC)
Motherboard: ASRock - Fatal1ty B450 GAMING K4 ATX AM4 Motherboard  ($98.99 @ Amazon)
Memory: G.Skill - Ripjaws V Series 16 GB (2 x 8 GB) DDR4-3000 Memory  ($104.99 @ Newegg Business)
Storage: Inland - 240 GB 2.5" Solid State Drive  ($29.99 @ Amazon)
Storage: Seagate - Barracuda 2 TB 3.5" 7200RPM Internal Hard Drive  ($59.89 @ OutletPC)
Video Card: PowerColor - Radeon RX 580 8 GB Video Card  ($179.99 @ Newegg)
Case: Deepcool - TESSERACT SW ATX Mid Tower Case  ($59.99)
Power Supply: SeaSonic - 520 W 80+ Bronze Certified Fully-Modular ATX Power Supply  ($56.61 @ Newegg Business)
Total: $760.34
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-01-12 22:13 EST-0500

PCPartPicker part list: https://pcpartpicker.com/list/XtnJD2
Price breakdown by merchant: https://pcpartpicker.com/list/XtnJD2/by_merchant/
CPU: AMD - Ryzen 5 2600 3.4 GHz 6-Core Processor  ($164.99 @ Amazon)
CPU Cooler: Corsair - H60 (2018) 57.2 CFM Liquid CPU Cooler  ($69.99 @ B&H)
Motherboard: ASRock - B450 Pro4 ATX AM4 Motherboard  ($64.99 @ Newegg)
Memory: G.Skill - Ripjaws V Series 16 GB (2 x 8 GB) DDR4-3200 Memory  ($130.98 @ Amazon)
Storage: Samsung - 860 Evo 500 GB 2.5" Solid State Drive  ($82.99 @ Amazon)
Storage: Western Digital - Caviar Blue 1 TB 3.5" 7200RPM Internal Hard Drive  ($44.89 @ OutletPC)
Video Card: PowerColor - Radeon RX 590 8 GB Red Devil Video Card  ($259.99 @ Newegg)
Case: Corsair - 200R ATX Mid Tower Case  ($49.99 @ Newegg)
Power Supply: EVGA - SuperNOVA G2 550 W 80+ Gold Certified Fully-Modular ATX Power Supply  ($57.89 @ OutletPC)
Total: $926.70
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-01-10 21:27 EST-0500

100000x ASRock. Not MSI. Never MSI.

If you do indeed want to overclock, then the Z390 Phantom. It's actually pretty good little board, very solid even more considering you will use the new gen intel 9K CPU that is pretty power hungry and it might even throtle if the VRMs reach a certain laod or temperature.
 
Play it safe...

If your friend wants to go further with overclocking, the ASRock Z370 Extreme4 is a great board for heavy overclocks and isn't super flashy. 

not even for this?
PCPartPicker part list / Price breakdown by merchant Type Item Price CPU AMD - Ryzen 5 2600 3.4 GHz 6-Core Processor $164.89 @ OutletPC CPU Cooler ARCTIC - Freezer 33 eSports ONE (Black/White) CPU Cooler $32.12 @ Newegg Motherboard ASRock - B450 Pro4 ATX AM4 Motherboard $64.89 @ OutletPC Memory G.Skill - Ripjaws V Series 16 GB (2 x 8 GB) DDR4-3000 Memory $104.99 @ Newegg Storage Samsung - 860 Evo 500 GB 2.5" Solid State Drive Purchased For $0.00 Storage Seagate - Barracuda 2 TB 3.5" 7200RPM Internal Hard Drive $59.89 @ OutletPC Video Card EVGA - GeForce RTX 2080 8 GB Black Video Card $698.99 @ SuperBiiz Case Fractal Design - Focus G (Black) ATX Mid Tower Case $57.66 @ Newegg Power Supply BitFenix - Formula Gold 550 W 80+ Gold Certified ATX Power Supply $59.99 @ Newegg   Prices include shipping, taxes, rebates, and discounts     Total (before mail-in rebates) $1263.42   Mail-in rebates -$20.00   Total $1243.42   Generated by PCPartPicker 2019-01-06 17:16 EST-0500    

this should do the job (pcpp germany btw, as dutch one only lists paradigit)
PCPartPicker part list / Price breakdown by merchant Type Item Price CPU AMD - Threadripper 1950X 3.4 GHz 16-Core Processor €567.99 @ Amazon Deutschland CPU Cooler be quiet! - DARK ROCK PRO TR4 59.5 CFM CPU Cooler €76.79 @ Aquatuning Motherboard ASRock - X399 Taichi ATX TR4 Motherboard €334.94 @ Mindfactory Memory G.Skill - Ripjaws V Series 32 GB (2 x 16 GB) DDR4-3000 Memory €254.00 @ Amazon Deutschland Memory G.Skill - Ripjaws V Series 32 GB (2 x 16 GB) DDR4-3000 Memory €254.00 @ Amazon Deutschland Memory G.Skill - Ripjaws V Series 32 GB (2 x 16 GB) DDR4-3000 Memory €254.00 @ Amazon Deutschland Memory G.Skill - Ripjaws V Series 32 GB (2 x 16 GB) DDR4-3000 Memory €254.00 @ Amazon Deutschland Storage Samsung - 860 Evo 1 TB 2.5" Solid State Drive €152.89 @ Mindfactory Video Card PNY - Quadro P4000 8 GB Video Card €764.94 @ Amazon Deutschland Case Fractal Design - Define S ATX Mid Tower Case €76.85 @ Amazon Deutschland Power Supply Corsair - HX Platinum 850 W 80+ Platinum Certified Fully-Modular ATX Power Supply €151.33 @ Mindfactory   Prices include shipping, taxes, rebates, and discounts     Total €3141.73   Generated by PCPartPicker 2019-01-06 23:35 CET+0100    

x470 fatal1ty would be great for you

Hello,i've listed the parts in here 
 
Note : i always recommend 16 GB of ram for new gaming build
PCPartPicker part list / Price breakdown by merchant Type Item Price CPU AMD - Ryzen 5 2600X 3.6 GHz 6-Core Processor $289.00 @ Canada Computers CPU Cooler Cooler Master - MasterLiquid ML240L RGB 66.7 CFM Liquid CPU Cooler $77.99 @ Canada Computers Motherboard ASRock - B450M-HDV Micro ATX AM4 Motherboard $66.77 @ Vuugo Memory Corsair - Vengeance LPX 16 GB (2 x 8 GB) DDR4-2400 Memory $137.99 @ Amazon Canada Storage Western Digital - Green 240 GB 2.5" Solid State Drive $53.75 @ Vuugo Storage Seagate - Barracuda 2 TB 3.5" 7200RPM Internal Hard Drive $69.95 @ Vuugo Video Card Zotac - GeForce GTX 1070 Ti 8 GB AMP Edition Video Card $548.00 @ Mike's Computer Shop Case Fractal Design - Focus G (Black) ATX Mid Tower Case $45.28 @ Amazon Canada Power Supply EVGA - SuperNOVA G3 750 W 80+ Gold Certified Fully-Modular ATX Power Supply $79.99 @ Canada Computers Operating System Microsoft - Windows 10 Home OEM 64-bit $119.50 @ Newegg Canada   Prices include shipping, taxes, rebates, and discounts     Total (before mail-in rebates) $1513.22   Mail-in rebates -$25.00   Total $1488.22   Generated by PCPartPicker 2019-01-03 23:25 EST-0500    

PCPartPicker part list / Price breakdown by merchant Type Item Price CPU AMD - Ryzen 3 1200 3.1 GHz Quad-Core Processor $139.87 @ Amazon Canada CPU Cooler ARCTIC - Freezer 13 CO 4 CFM Ball Bearing CPU Cooler $45.99 @ Newegg Canada Motherboard ASRock - AB350M Pro4 Micro ATX AM4 Motherboard $104.99 @ Newegg Canada Memory Corsair - Vengeance LPX 16 GB (2 x 8 GB) DDR4-2400 Memory $137.99 @ Amazon Canada Video Card Gigabyte - GeForce GT 1030 2 GB Silent Low Profile Video Card $109.99 @ Amazon Canada Case Corsair - Carbide Series 88R MicroATX Mid Tower Case $54.99 @ Canada Computers Power Supply EVGA - SuperNOVA G3 550 W 80+ Gold Certified Fully-Modular ATX Power Supply $69.99 @ Canada Computers Optical Drive Asus - DRW-24F1ST DVD/CD Writer $21.50 @ Vuugo   Prices include shipping, taxes, rebates, and discounts     Total $685.31   Generated by PCPartPicker 2019-01-03 21:15 EST-0500   I think this is everything I need. and it's under my budget by about fifty dollars.

PCPartPicker part list / Price breakdown by merchant Type Item Price CPU AMD - Ryzen 5 2600 3.4 GHz 6-Core Processor $229.99 @ Amazon Canada Motherboard ASRock - B450M PRO4 Micro ATX AM4 Motherboard $77.63 @ Vuugo Memory Team - Vulcan 16 GB (2 x 8 GB) DDR4-3000 Memory $129.99 @ Newegg Canada Storage Kingston - A400 240 GB 2.5" Solid State Drive $45.99 @ Memory Express Storage Western Digital - Caviar Blue 1 TB 3.5" 7200RPM Internal Hard Drive Purchased For $0.00 Video Card Gigabyte - Radeon RX 580 8 GB AORUS 8G Video Card $229.99 @ Memory Express Case Cooler Master - MasterBox Q300L MicroATX Mini Tower Case $54.75 @ Vuugo Power Supply Corsair - CX (2017) 450 W 80+ Bronze Certified ATX Power Supply $39.99 @ Canada Computers   Prices include shipping, taxes, rebates, and discounts     Total (before mail-in rebates) $838.33   Mail-in rebates -$30.00   Total $808.33   Generated by PCPartPicker 2019-01-03 19:37 EST-0500   you can get this for just 100 bucks more...

Wait after CES. We will have info on Zen 2.
 
Also. For tye price you can get a threadripper system
 
PCPartPicker part list / Price breakdown by merchant
CPU: AMD - Threadripper 1950X 3.4 GHz 16-Core Processor  ($548.89 @ OutletPC) 
CPU Cooler: Noctua - NH-U14S TR4-SP3 82.52 CFM CPU Cooler  ($79.90 @ Amazon) 
Motherboard: ASRock - X399 Taichi ATX TR4 Motherboard  ($259.99 @ Newegg) 
Memory: G.Skill - Ripjaws 4 series 32 GB (4 x 8 GB) DDR4-3000 Memory  ($229.99 @ Newegg) 
Storage: Crucial - MX500 1 TB 2.5" Solid State Drive  ($129.00 @ Amazon) 
Storage: Western Digital - Black 4 TB 3.5" 7200RPM Internal Hard Drive  ($177.99 @ SuperBiiz) 
Video Card: EVGA - GeForce RTX 2080 8 GB Black Video Card  ($698.99 @ SuperBiiz) 
Case: NZXT - H500 (Black) ATX Mid Tower Case  ($69.99 @ Amazon) 
Power Supply: SeaSonic - FOCUS Plus Gold 850 W 80+ Gold Certified Fully-Modular ATX Power Supply  ($104.99 @ Newegg) 
Total: $2299.73
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-01-02 15:53 EST-0500

PCPartPicker part list / Price breakdown by merchant Type Item Price CPU AMD - Ryzen 5 1600 3.2 GHz 6-Core Processor £129.19 @ Aria PC Motherboard ASRock - AB350M Pro4 Micro ATX AM4 Motherboard £65.78 @ CCL Computers Memory Corsair - Vengeance LPX 8 GB (1 x 8 GB) DDR4-2400 Memory £52.38 @ Aria PC Storage Western Digital - Caviar Blue 1 TB 3.5" 7200RPM Internal Hard Drive £34.99 @ Amazon UK Video Card Gigabyte - Radeon RX 580 8 GB Gaming 8G Video Card £199.97 @ Ebuyer Case Corsair - 200R ATX Mid Tower Case £57.98 @ PC World Business Power Supply Corsair - CXM 550 W 80+ Bronze Certified Semi-Modular ATX Power Supply £70.68 @ Amazon UK   Prices include shipping, taxes, rebates, and discounts     Total £610.97   Generated by PCPartPicker 2019-01-03 00:57 GMT+0000    

Lets see, for less he can have a better CPU Ryzen 7, better storage and better graphics...
 
PCPartPicker part list: https://uk.pcpartpicker.com/list/HXJT7W
Price breakdown by merchant: https://uk.pcpartpicker.com/list/HXJT7W/by_merchant/
CPU: AMD - Ryzen 7 1700 3 GHz 8-Core Processor  (£145.93 @ Aria PC)
CPU Cooler: Cooler Master - Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler  (£23.00 @ PC World Business)
Motherboard: ASRock - B450M PRO4 Micro ATX AM4 Motherboard  (£76.49 @ CCL Computers)
Memory: G.Skill - Aegis 16 GB (2 x 8 GB) DDR4-3000 Memory  (£120.89 @ Alza)
Storage: Kingston - A400 240 GB 2.5" Solid State Drive  (£31.98 @ Aria PC)
Storage: Western Digital - Caviar Blue 1 TB 3.5" 7200RPM Internal Hard Drive  (£34.99 @ Amazon UK)
Video Card: PowerColor - Radeon RX 580 8 GB Video Card  (£190.79 @ Amazon UK)
Case: Apevia - X-QTIS-BK MicroATX Mid Tower Case
Power Supply: Corsair - CXM (2015) 450 W 80+ Bronze Certified Semi-Modular ATX Power Supply  (£42.64 @ Amazon UK)
Total: £666.71
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-12-29 04:44 GMT+0000

Thats right, the Ryzen likes faster memory. But don't over spend on memory.

Here's my Intel recommendation:
 
PCPartPicker part list / Price breakdown by merchant Type Item Price CPU Intel - Core i5-8400 2.8 GHz 6-Core Processor $220.98 @ Newegg Motherboard ASRock - B360 Pro4 ATX LGA1151 Motherboard $83.98 @ Newegg Memory Crucial - Ballistix Sport LT 16 GB (2 x 8 GB) DDR4-2666 Memory $96.99 @ Amazon Storage Samsung - 860 Evo 500 GB 2.5" Solid State Drive $72.00 @ Amazon Video Card MSI - Radeon RX 580 4 GB ARMOR OC Video Card $277.57 @ Amazon Power Supply Corsair - CXM 550 W 80+ Bronze Certified Semi-Modular ATX Power Supply $59.89 @ OutletPC   Prices include shipping, taxes, rebates, and discounts     Total (before mail-in rebates) $831.41   Mail-in rebates -$20.00   Total $811.41   Generated by PCPartPicker 2018-12-10 21:49 EST-0500    

Spend a tiny bit more for a decent SSD. Worth every penny.
 
PCPartPicker part list / Price breakdown by merchant Type Item Price CPU AMD - Ryzen 5 2600 3.4 GHz 6-Core Processor $159.99 @ Amazon Motherboard ASRock - AB350M-HDV Micro ATX AM4 Motherboard $56.39 @ OutletPC Memory Crucial - Ballistix Sport LT 16 GB (2 x 8 GB) DDR4-2666 Memory $96.99 @ Amazon Storage ADATA - Ultimate SU800 256 GB 2.5" Solid State Drive $44.99 @ Amazon Video Card Zotac - GeForce GTX 1060 6GB 6 GB Mini Video Card $209.99 @ B&H Case Rosewill - FBM-X1 MicroATX Mini Tower Case $24.99 @ Amazon Power Supply EVGA - BT 450 W 80+ Bronze Certified ATX Power Supply $29.89 @ OutletPC   Prices include shipping, taxes, rebates, and discounts     Total (before mail-in rebates) $643.23   Mail-in rebates -$20.00   Total $623.23   Generated by PCPartPicker 2018-12-10 22:27 EST-0500    

Owner of an AB350M, each slot is its own channel, so no worries if you want to run in dual-channel.

PCPartPicker part list / Price breakdown by merchant Type Item Price CPU AMD - Ryzen 7 2700 3.2 GHz 8-Core Processor $399.00 @ Shopping Express CPU Cooler be quiet! - Dark Rock Pro 4 50.5 CFM CPU Cooler $119.00 @ PCCaseGear Motherboard ASRock - Fatal1ty X470 Gaming K4 ATX AM4 Motherboard $247.02 @ Amazon Australia Memory Corsair - Vengeance LPX 16 GB (2 x 8 GB) DDR4-3000 Memory $202.00 @ Amazon Australia Storage Samsung - 860 Evo 500 GB 2.5" Solid State Drive $111.00 @ JW Computers Storage Seagate - Barracuda 3 TB 3.5" 7200RPM Internal Hard Drive $125.00 @ PLE Computers   Prices include shipping, taxes, rebates, and discounts     Total $1203.02   Generated by PCPartPicker 2018-11-14 22:45 AEDT+1100   here you go

PCPartPicker part list / Price breakdown by merchant Type Item Price CPU AMD - Ryzen 3 2200G 3.5 GHz Quad-Core Processor $92.68 @ Amazon Motherboard ASRock - X470 Taichi ATX AM4 Motherboard $203.98 @ Newegg Memory G.Skill - Flare X Series 16 GB (2 x 8 GB) DDR4-3200 Memory $199.89 @ OutletPC Storage Samsung - 860 Evo 500 GB 2.5" Solid State Drive $72.99 @ Amazon Video Card MSI - Radeon RX 580 8 GB ARMOR MK2 OC Video Card $219.99 @ Newegg Case NZXT - H500 (Black) ATX Mid Tower Case $69.99 @ B&H Power Supply EVGA - SuperNOVA G2 750 W 80+ Gold Certified Fully-Modular ATX Power Supply $89.89 @ OutletPC   Prices include shipping, taxes, rebates, and discounts     Total (before mail-in rebates) $999.41   Mail-in rebates -$50.00   Total $949.41   Generated by PCPartPicker 2018-12-05 19:13 EST-0500    
i wouldn't cheap out on motherboard, who knows if amd will give us a 150w zen 2 (the 2700x cooler is already 135w)

Something like this? Prices are from Germany so maybe some stuff may be more expensive if you're not from germany.
 
PCPartPicker part list / Price breakdown by merchant
CPU: AMD - Ryzen 5 2600 3.4 GHz 6-Core Processor  (€157.90 @ Mindfactory) 
Motherboard: ASRock - B450 Pro4 ATX AM4 Motherboard  (€85.99 @ Amazon Deutschland) 
Memory: Corsair - Vengeance LPX 16 GB (2 x 8 GB) DDR4-3000 Memory  (€122.90 @ Amazon Deutschland) 
Storage: Crucial - MX500 500 GB M.2-2280 Solid State Drive  (€71.90 @ Amazon Deutschland) 
Video Card: Sapphire - Radeon RX VEGA 56 8 GB NITRO+ Video Card  (€399.00 @ Amazon Deutschland) 
Case: Fractal Design - Define S ATX Mid Tower Case  (€76.90 @ Amazon Deutschland) 
Power Supply: SeaSonic - FOCUS Plus Gold 550 W 80+ Gold Certified Fully-Modular ATX Power Supply  (€78.99 @ Amazon Deutschland) 
Total: €993.58
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-12-04 04:06 CET+0100
 
I didn't grab an NVMe SSD because for what you'll be doing (storing OS, apps, games, etc.) it's really not worth it. There will be little to no difference between an NVMe ssd and a solid SATA SSD like the mx500
 
https://techreport.com/review/30813/samsung-960-pro-2tb-ssd-reviewed/5
 
I chose a Vega 56 because your monitor has freesync, so I think that'd be a good thing to take advantage of. Also, you might have some options for the case. I'm not sure if you want a window or not or what specific aesthetics you'd like so I just chose the define s which is a pretty solid all around case. If you want something more flashy (or with rgb?) or with a windows you might want something else.