Basic gaming components
So for all of all of these the basics are mostly the same for them as a home computer.
CPUs
For CPUs you will want to get a very fast one with hyper threading and possibly the ability to overclock it.
Motherboards
For a motherboard you'll need one that at least supports dual core processors. A good gaming motherboard would be probably be a MSI high performance motherboard.
RAM
For ram you'll probably want to have at least 16 GigaBytes for best performance and DDr4 RAM for serious performance gaming but if you want to go completely overkill you can see LinusTechTips do it with 128Gigabytes of DDr4 RAM!
Power Supply
power supplies are pretty much the same for a gaming computer aside from the sleeker design the more wattage and modular support. Modular support is when you can add more cables for more things like hard drives it looks like this...
Hard Drives
For hard drives you need to think of things a little bit differently. For top performance you'll wan't an SSD but the thing about getting an SSD they are much faster than a regular hard drive but the more space you want the more expensive they get whereas compared to a hard drive, they are very cheap for more space. So you might want to get a hybrid drive or both a SSD and a hard drive to have the SSD handle the operating system and applications the rest of the big stuff for the hard drive to store.