so right now im using a nvidia 9500 GT with 2 GB of ram and 149 GB of memory, and a Intel(R) Pentium(R) D CPU 3.00 GHz. I think i have two also so what would need to be upgraded to showsubstantial benifits, thanks.
Like they said, you have an older system with many relatively slow parts. You can improve it without wasting money if you buy parts you can re-use in your next computer (when you build it). High on that list is an improved GPU and the PSU needed to power it. You've not provided your current PSU (brand and model as well as wattage), but most likely it will need to be replaced. Just about any single graphics card will run on a quality 500W-550W PSU. A quality modern PSU has full range active PFC (no little voltage switch), and 80+ certification for efficiency. Antec, Seasonic, Corsair, XFX, and Enermax are among the better brands. Then, depending on your budget, resolution, and games, get a new GPU. At minimum, a HD5770 will play most games with good (not necessarily max) detail. A HD6850 or 1GB GTX460 would be a good step up, and a HD6950 or GTX560Ti another step up from that. Any of these cards will be severely bottlenecked on your current system, although they should show some improvement; what's important is that you won't have wasted any money, as you'll re-use the new PSU and GPU in your next PC.
By contrast, adding RAM may offer some improvement as well, but would likely be a waste, as the type will be obsolete, whether DDR or DDR2. It may only be $40 or so, but a waste is a waste.