Well onboard video is the absolute worst you can do. So the skies are only clearer from here (that is if you upgrade to a video card). $50 won't really bring you much of an improvement. $100, probably yes.
For $70, the ATI 2600 Pro is probably your best bet.
For $100, either the Nvidia 8600GT or the ATI 2600XT
The +$30 is going to give you maybe 10-15 FPS on fairly low resolutions.
Do you know what kind of processor you have?