Return of Reckoning

Hello everyone!
I'm so stoked that this is a thing as I've just pulled a P.O.S pc out of my trunk and to my surprise it booted perfectly. The game runs fairly well, but in high pop zones and pop I won't have such luck. Here's the specs
Amd processor (I know)
500gb hdd
4gb RAM
280 w power supply

I'm sure you noticed there's no video card. I'm planning on completely replacing the computer with a custom build, but for the time being I wanted to get a video card to hold me over until then. Suggestions would be greatly appreciated!

the game is not optimized, so all computers have trouble in huge fights, its not just the graphic card that would need to be upgraded to perform much better

What games are you planning to play? Only RoR and other MMOs? Or more demanding games? Batman,Gta v etc etc.
Tell me your budget and i can help you.