Bastola

CPU: AMD Ryzen 5 3600 3.6 GHz 6-Core Processor  ($194.79 @ OutletPC) 
CPU Cooler: Noctua NH-D15 CHROMAX.BLACK 82.52 CFM CPU Cooler  ($99.95 @ Amazon) 
Motherboard: MSI B450 TOMAHAWK MAX ATX AM4 Motherboard  ($114.99 @ Amazon) 
Memory: Corsair Vengeance LPX 16 GB (2 x 8 GB) DDR4-3200 Memory  ($82.89 @ OutletPC) 
Storage: Crucial P1 1 TB M.2-2280 NVME Solid State Drive  ($95.99 @ Amazon) 
Storage: Seagate Barracuda 2 TB 3.5" 7200RPM Internal Hard Drive  ($64.89 @ OutletPC) 
Video Card: Sapphire Radeon RX 5700 XT 8 GB NITRO+ Video Card  ($459.00 @ Amazon) 
Case: Fractal Design Meshify C ATX Mid Tower Case  ($89.99 @ Amazon) 
Power Supply: Corsair RMx (2018) 650 W 80+ Gold Certified Fully Modular ATX Power Supply  ($109.99 @ Amazon) 
Operating System: Microsoft Windows 10 Home OEM 64-bit  ($99.95 @ Amazon) 
Total: $1412.43
 
how about something like this?
that even incliudes a full price copy of windows and has 80 bucks left for additional fans and rgb should you be into that.

Hiya! I highly recommend that you take a look at pcpartpicker.com. 
It's a great tool used to track what components are being used in a build and to check for basic compatibility. 

1700 what? Dollars, rupees, cat hairs?

PCPartPicker Part List
CPU: AMD Ryzen 7 3700X 3.6 GHz 8-Core Processor  ($329.00 @ B&H)
CPU Cooler: ARCTIC Freezer 34 eSports CPU Cooler  ($33.99 @ Amazon)
Motherboard: Asus ROG STRIX B450-F GAMING ATX AM4 Motherboard  ($126.89 @ OutletPC)
Memory: G.Skill Ripjaws V Series 16 GB (2 x 8 GB) DDR4-3200 Memory  ($67.99 @ Newegg)
Storage: ADATA XPG SX6000 Pro 256 GB M.2-2280 NVME Solid State Drive  ($39.99 @ Amazon)
Storage: Crucial BX500 960 GB 2.5" Solid State Drive  ($99.89 @ OutletPC)
Video Card: MSI GeForce RTX 2080 8 GB GAMING X TRIO Video Card  ($649.99 @ B&H)
Case: Fractal Design Define R5 (Black) ATX Mid Tower Case  ($137.53 @ Amazon)
Power Supply: SeaSonic FOCUS Plus Platinum 550 W 80+ Platinum Certified Fully Modular ATX Power Supply  ($109.99 @ Amazon)
Total: $1595.26
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-08-05 12:01 EDT-0400

if you want to develop video games and you"re worried about catering to various operating systems  then you should use a KVM solution.  Using UnRAID or Proxmox as your base operating system then virtualizing the target operating systems.  You can limit the core count and impact how much RAM/CPU compute units will be readily available to the VM.  You can even go about simulating the various storage solutions for each VM.  If you want to simulate the iGPU that most macbook pros have then just get an underpowered AMD GPU.  If you put your motherboard in UEFI boot mode (csm compatibility off) then you can have 3 GPUs.  One GPU for your base operating system.  One GPU for "high performance" and one GPU for "low-mid tier performance".  If you do go this route I suggest using Team Red's platform as it will be less confusing because of the maturity of the 64 bit stack.  If you forgo having some peripheral PCI-E device then you have 4 GPUs.  1 GPU for high performance, 1 GPU for mid tier performance, 1 GPU for low end performance and 1 GPU to get your system to POST.  You'll need a pci-e x1 graphics card to make this feasible (https://www.amazon.com/ZOTAC-GeForce-Profile-Graphic-ZT-71304-20L/dp/B01E9Z2D60/ref=sr_1_1?keywords=pci-e+x1+gpu&qid=1564784905&s=gateway&sr=8-1).  As a side effect this will also empower you to develop for the various distributions of linux with minimal effort.
 
I've found that this works relatively well for application deployment.  Mira does have a point though, if you want to make sure your system work on an Apple platform, you will need an Apple platform (although I've yet to run into this problem).

If you're going to target macOS for your applications, then you need a macOS machine. You can still use Bootcamp to test on Windows. Otherwise whatever OS fits your taste and whatever hardware fits your requirements.
 
Before anyone suggests "Hackintosh", I'd advise against that because Hackintoshes will likely not represent the target environment of a given macOS user, and it's extremely important to be able to test on an actual target system.

if it is free then it is for me. 

There is a lot to think about.

JS / C# or C++
Focus on 2D or 3D?
Free or paid?

I would say unreal as it is free. Though if C# is important for you Godot is free and open-source.

Unity is much easier. Unreal is more powerful and more optimized.