the sticky helps you to let us know what you want from your system.
but i'll try to answer what you are asking for.
for a good gaming rig you will need a relativly good CPU and a good GPU
for your budget i will look into AMD
CPU phenom x4 955
Ram 4g is enough
PSU 650w Corsair, Seasonic and Antec are good PSUs
HDD Samsung spinpoint F3 1tb should be good
GPU depends on the total build price either 5770 or 5850 (5850 is more future proof but a lot more in price
Mobo pick Asus or Gigabyte
Case Antec 300 illusion (only sold at newegg), Antec 900 is what i have and is good
Since when I joined I wouldn't have understood the instructions so far (and a rephrase for clarity can't hurt)
The link's to a thread in the forum about how to post for new build advice. It gives a useful layout that helps people on the forum recommend components that suit what you're looking for.
and btw, the stuff underneath the link is a signature, which is like a little message that you choose to have automatically put underneath your post (if you want to know how, go to your profile, forum options) and if a thread has been stickied, it's been placed at the top of the forum because it's been deemed as essential / very useful / very helpful.
hope that helps and sorry if you know what I'm talking about and it seems a bit dumbed down.