The GPU is responsible for all the graphics rendering. A faster GPU will make video display smoother, enable advanced desktop enhancements, and allow for smooth(er) video gaming.

Depends on your purpose and Screen size

Gaming on 1080p will requires a 250$+ Gpu

Gaming on 720P will require 130$+ gpu

tell me your system specs and your purpose i will suggest a good one

First I need to know what brand of game card.

iPhone 5's new A6 offers an impressive triple core dedicated GPU

gpu is a graphical processing unit which ables you run high definitions graphics on your PC, which are the demand of modern computing. if you want to run windows vista ultimate edition then it is better if your PC has a gpu. it helps you to get better 3d views. nividia is very well known for it's gpu.