Spynapple

yea your going to have to supply more info
price point
room size
do you want 5.1.2 or up to 7.1.4
 
most costly will be an avr.....denon, yamaha, or marantz would be my top 3 (oh and depending on amount of speakers will determine cost of avr, once you go past 7.1 or 5.1.2 the avrs jump in price AND some require a external amp to run 2 speakers)
speakers ....center and left/right are most important.......majority of audio goes to center. left/right because of stereo dont go cheap on these
surrounds....they dont work as hard as the c-l-r speakers but i highly recommend bi-polor speakers
atmos.... that can be an issue because they are ceiling speakers. if you dont have attic access much less able to run the wires up to them. then the ones that bounce sound on the ceiling will have to do. (unless you mount speakers boxes to the ceiling but wont look good)
 
and you dont need to get everything right away AND all the speakers dont need to be the same company or set either.(i have a jbl center, yamaha left/right, fluance surrounds, yamaha atmos, alpine sub - 7.1.4 all said and done mine ran about 3000)

I would start with 7.1 (5.1.2) AV receiver. If you never experience 5.1 surround before, start from there then add two height channels later. If you're low on budget you can buy second hand AVR that is made between 2015-2017 that has Atmos and DTS:X support, or 2018-2019 if you need eARC. HDMI 2.1 AVRs are waste of money unless you need them for gaming and don't wanna go through hoops (like I did). 
 
As for gaming, I'm the only person on Earth that cares but... don't get Yamaha AVR. I previously had two of them and both had bad audio latency for Stereo PCM (multi-channel PCM were unaffected), worse if it's on 48khz sample rate instead of 192khz (affects both stereo and multi-channel PCM). My current AVRs are Denon x3400h which has excellent audio latency, and Marantz SR7013 has okay latency, unless setting to 192khz on PC. 

My wife watches a lot of movies and we both aren't comfortable using headphones. I am planning for Atmos as I heard it is better than 5.1 surround. Plan is to use the same system for gaming and watching movies and shows.
 
Thing is I have no clue about what all I would need for this.

What's your budget, what is your desired goal?

I have a 7.2.4 Atmos based set up, it cost around $3000ish. Doing atmos well will cost at a minimum $1200 USD with TONS of corners cut. You'll also have more complexity vs a 2.1 set up. ($400 AVR, $300 used subwoofer, $200 front speakers, $100 side speakers $100 top speakers, $50 misc). This assumes speaker stands/mounts are free or not required and installation is free and that you're able to find stuff on sale and you're also skipping the center channel.

If this seems like a high value to you, I'd suggest considering an "OK" 2.1 set up first ($70 amp, $200-250ish front speakers, $300 used subwoofer - think Aiyima A07, Emotiva B1+, used SVS PB12 NSD/PB1000, speaker wire, a set of RCA cables and a piggback RCA cable so both the amp and the subwoofer can get the same signal- then set the subwoofer crossover to the drop off point for your speakers, probably between 50-80Hz). This is MUCH easier to get going and far more idiot proof. Worst case scenario you flip the amp and expand later. 

If you're going to atmos then kind of the cheapest AVR to look at would be the Denon S760h (sometimes on sale at Costco) and from there Emotiva B1+/JBL 530/KEF Q150 are all decent L+R contenders when on sale for 200-250ish. Then a subwoofer (rule of thumb, anything SVS, Rel, Monolith, Hsu, Outlaw). The side/rear/height speakers matter the least and can be small/inexpensive. I'm using 4 satellite speakers from a Klipsch Quintet kit a family member wasn't using. For the side speakers I'm mounting a pair of ELAC Debut OW4.2s to the wall. If using an AVR, set the subwoofer to NOT have a crossover or set the crossover to max (e.g. 180Hz)

what you generally need for home theater setups using at mos is a REciever and one capable enough to run whatever speakers you end up going with. 5.1 and 7.1 surrounds are pricey if you wanna build the system from the ground up there are sound bar solutions that aim to be alternatives but often dont sound as good as true 7.1 and 5.1 surround setups. my suggestion is to shop around to get an idea of what is considered good speakers for such a setup and what is considered a good reciever and the ever important ".1"  the subwoofer can also be a unexpected expensive piece total that up to get an idea of a budget. the cheapest iI've seen to be quite decent is a $1000 and thats considered budget. also look into the local used market as thats a good way to save on speakers and dont  be afraid to mix and match especially on the rear speakers
 

What is your use case?  Personally 5+ years ago when I was running on a home theater daily, the surround was almost never used.  The only time it was put into action was while watching movies.
 
The issue being that you need an Atmos sound track to use Atmos.  I'm unsure if games offer this feature these days but surround was not really a thing in the games I played let alone atmos.
 
My thought on this subject is that game developers are usually spread thin enough that they can't put the effort into something that a fraction of a percent of their player base might make use of.
 
I would look into a good headphone + mic or 2.1/2.0 setup and call it a day, you'll get something way better if the budget is spent on 2 speakers a dac and an amp vs 5+ speakers

http://www.jongerow.com/Corsair_PSU_hierarchy/index.html

Both are very high quality, but the HX750 has a higher 80+ rating (platinum vs gold) At the same price, I would buy the HX750.