@Officer Hotpants
That’s fully understandable. You do need to know enough to read and understand the motherboard’s spec sheet. And there are little things like a lot of the high-powered gaming video cards having separate power connectors to connect them to the power supply. If they’re not connected correctly, it may try to pull the power it needs through the motherboard, which can damage it.
And some of the really high-end gaming video cards draw enough juice to run a small arc welder, so you will need a power supply that has the auxiliary connections for that and can give them the juice they need–and you will need to plug the PC into a socket on the wall that will give it the amperage it needs and not trip the circuit breaker when you start up a game.
As I said, none of this is rocket science. Most of the parts, these days, only fit one way. But you will need to be sure all the parts are compatible. Laptops and desktops use different types of memory that aren’t interchangeable, and it isn’t necessarily obvious which kind it is when you’re holding it in your hand. And so on. Maybe go to a brick-and-mortar computer store and show them the motherboard spec sheet and tell them “I’m doing a desktop build, and this spec sheet says I need DDR4, do you have four eight-gig sticks of DDR4 so I can get 32 gigs?”
As an aside, in most PCs, for most users, processing power is a solved problem. It was a solved problem twenty-five years ago, for reading email, and looking at Internet memes. Gaming is more demanding, though how demanding is dependent on the games you play. Most games lean much harder on the video card, calculating shading and texturing and so on, and the processing load goes up geometrically with higher resolutions–the video cards that could produce playable video at 1024x768 flounder and stutter at 4K. Driving sims and flight sims lean harder on the CPU, calculating multiple physics models and running multiple AIs in realtime.
You will generally get what you pay for–but for most gaming, RAM is a bottleneck and the more of it you have, the less time the OS will spend loading additional data from the HDD. For a 64-bit OS, 4GB is good for web surfing and emailing, 8GB handles most office software pretty well, 16GB and up may help performance with gaming. Like more CPU cores, more RAM is better than less, with no downside to having more other than cost.
The basic shopping list is:
case
power supply
motherboard
CPU, will almost certainly come with an adequate heat sink, there are aftermarket heat sinks too
RAM
at least one main storage drive, which can be an HDD (inexpensive, mediocre performance, spacious for the money) or SSD (expensive, small storage space for what you pay, very fast), some like the combination of a smallish SSD for the OS to boost performance and a big cheap HDD for storing lots of stuff
optical drive, like a DVDRW maybe
video card (some video cards are designed to be used in pairs for parallel processing and increased performance; this is expensive and extremely power-hungry, and not every motherboard supports it, so how much do you want to spend here? like they say in the auto racing business, speed costs money, how fast do you wanna go?)
You’ll need some kind of monitor if you don’t have one. For gaming look for high refresh rates, like 60 Hz and above.
Lots of stuff that you used to have to buy separately and add in, like a network card, or a sound card, are normally built into the motherboard now. Most motherboards have onboard video too, but it’s only going to be just good enough for looking at cat videos on the Internet and sending email. Onboard video is not for gaming. Some audio enthusiasts still buy separate sound cards and put them in but that’s a shrinking market these days.
Once you assemble everything, and you have the operating system you want on bootable media (CD, DVD, thumbdrive, whatever) you power it up and, after it POSTs, go into the BIOS settings and set it to boot from the device with the media, and plug in the thumbdrive or put in the disc. Then reboot and follow the prompts on the screen.
Assuming that this is to be a Windows box, which would be expected for gaming, you would, once you are able to boot into the OS and get to the desktop… well, just on general principles, in Windows I like to make a normal user account that will be used to do 99% of stuff and a separate admin account, which I never log into if I don’t have to. It reduces the chances of a virus being able to do a lot of damage if I use the normal user account and just put in the admin password when prompted to do various things. Once that’s done, run Windows Update and get everything it needs, unless people in tech forums are saying “don’t get this week’s Windows patch, it bricked my computer.” Then go to the web page of the manufacturer of your video card and download and install the most current driver software for your video card.
Then maybe run disk cleanup and do a defrag. If you prefer to have the data compressed or encrypted on the HDD, now is the time to get those settings put in.
It’s a bit tedious and fiddly. There is a reason most people go to the Dell web page or whatever and get a prebuilt box. But it’s definitely doable.
For a gaming desktop currently I’d recommend an Intel i5 or higher, or a Ryzen 5 if you’re an AMD fanboy. I recommend no less than 16GB of RAM for a gaming system, and there’s nothing wrong with 24 or 32 gigs–or more, though we might be getting to the point of diminishing returns.
Due to disruptions in the supply chain resulting from the Chinese flu, prices on all components generally and video cards in particular are extremely inflated right now, but will probably come down in the next few months, barring infinite additional lockdowns for Thuh Delta Variant, or Thuh Sigma Variant, or Thuh Ligma Variant. And all this changes constantly. You might look at web pages like
this for guidance on price-performance for video cards currently on the market.
Or you could just get a prebuilt gaming system from Dell, or Alienware, or insert your favorite brand here.