One thing I did when I started my 1st build was to go to a site like Alienware and walk thru a specific machine they had offered. See what they used and how they matched up there parts choices.
Then I researched their choices in different forums and online stores. This helped me familiarize myself with stuff. Gave me an inkling on what to look for when it came to a gaming machine. My mom now uses that same machine. I had to get a new mobo at one point cuz it died. But all the other components are still functioning.
I was totally puter illiterate at the time. Just do not rush. My 2nd build was quite frustrating cuz the mobo was a ASUS Stryker Extreme, at the time, unbeknownst to me, there was a bunch of bad capacitors being used. The mobo was RMA'ed 4 times. Learned a lot there. This caused me to build my 3rd machine, it has been brilliant. Then I went back and revamped the the 2nd build, I use it as a bench/backup for my current one.
Just do not get caught in the latest and greatest loop. More expensive, more probs.
Remember for gaming its about the GPU and ram and getting a cpu that can handle them. If you choose an SSD for the OS, there are also things to make yourself aware of when it comes to the OS install and basic day to day use.
If you choose a PCI-e 3.0 vid card, make sure mobo has PCI-e 3.0 slots, make sure the mobo has onboard sound or you will need to purchase a sound card, make sure the PSU can handle the vid card and other components.
Also, you might consider buying the OS now. Many Xmas sales happening. Newegg has W7 64bit w/SP1 for $125. Good price, Newegg very good place. Shop around, you might find it cheaper. Do not buy from Amazon or E-Bay. Might seem like a good price, but who knows about the seller. You want it in an unopened MS box. Then treat the disc like its made of gold. Anytime your OS crashes or is corrupted, just erase drive and do a clean install. Best way to go.
research, research, research
luck