Low budget rig for gaming

Critique. Taking it from the top.

i3 2120 is not worth the money over a 2100.
Z68 board is useless with an un-overclockable i3.
That PSU cant run that GPU (not for long, anyway).
32bit OS wont work with 4GB of RAM.

Check my sig for a better idea of what to get.

+1 to Zero. How much are you looking to spend on the build anyway? What parts do you already have? What resolution are you going to play at? (more than 1024/768? if so a cheaper alternative may be AMD).

Great choices. IMO the i3-2120 is certainly worth the money over the 2100 if your running more than 1 high end video card, but your not.

Z68 gives you Ivy Bridge upgrade ability, future overclocking ability, and future sli/xfire ability, so might as well stick with the 2100.

The psu is cheap, but it'll work. Looks like a good build.

IMO, Buying a Z68 isn't a waste of money, as he can upgrade to a i5/i7 or even a Ivy Bridge processor in the future.

Get the Corsair CX430 or 500.