i am going to buy a new vga card for my computer what vga card should i buy?
You don't have much options here as your CPU will bottleneck most new cards. Your best bet is to go with a HD 7750 or a HD 7770. You'll need a pcie x16 or x8 to plug in the cards also you will be needing a 300- 350 watts PSU.
no his cpu is not an issue. it can even handle cards upto a 7850 easily.
it depends on his budget and his screen resolution.
taking a guesa if his screen resolution is 720p or 1600*900 then a 7770 would be more than enough. however if its 1080p then a 7850 will be required. so its either 7770 or 7850. anything higher will be bottlenecked