Video & Online Gaming: How to go about Building a Gaming PC?

Might be old, had this set-up since 2009

Currently these are the specs I have:
Model: Presario CQ62 Notebook PC
Processor: Intel (R) Celeron (R) CPU
900 @ 2.20GHz 2.19 GHz
RAM: 2 GB
System: 64-Bit Operating System

My system runs Window 7,

Curious on how to build a Gaming PC, any advice, price range; ect would be welcome.

Added (1). I see;

Added (2). *

Added (3). Appear

$320 very light gaming with an amd a8 build. Team fortress 2, flash games, minecraft.
$450 medium gaming with pentium and gtx 750 ti. Boyfriend low-medium settings and most games
$650 heavy gaming with fx 8320E and r9 280. High setting battlefield, can play all current games at least medium. Vast majority on high or ultra.
$1000- ultra high end with intel i5 and gtx 970. Everything on high or max, will be that way for a couple years.

I went to micro center and bought a lenovo laptop for 1k. 2 nviidia gtx 750 graphics cards 8gb ram 1tb hd quad 17 windows 8 64 bit and decent screen size. Tanks through any game i play. There are a lot of nice stock pcs for gaming
Games i play
Cod skyrim tf2

Go to walmart

Check out the below URLs to know more about the best resources for your query:

http://www.wikihow.com/Create-a-Gaming-Computer
http://lifehacker.com/...0-and-1200
http://graphics-cards-review.toptenreviews.com/learning-to-build-a-gaming-computer.html