What do I need to look for in a good gaming graphics card?

Hello

I am looking for a cheap graphics card ($110 or £70 at the most) for my first gaming desktop PC. I have virtually no clue what I am looking for, so any help pointing me in the right direction is appreciated. I hope to be able to play any of the high end games (Crysis for example) without any problems.

If there is anything specific you need to know about the rig, let me know.

Thanks for the help.