Looking for a fix for low gaming fps

[Waters001]

Computer Specs

ASUS P5E-VM DO

Intel quad core- 2.4GHz

ATX 500w

Ram DDR2 4Gb

Seagate HD 320Gb

Geforce 630 1Gb

Running windows 8.1

I bought this computer off of craigslist and i have no idea what the next steps to take would be to make this computer a atleast usable gaming computer. I try and play simple games like gmod or dayz and it will only get about 5-10 fps.

 

[CTurbo]

Do you have a budget for upgrades?

 

[Waters001]

I would like to keep it as cheap as possible but am willing to spend