When looking to upgrade graphics cards I personally look to a game I want to play, like the next Hitman game. I check out what cards it needs to run and then buy that or the equivalent 6-12 months after release.
So my only advice would be, if you have a higher spec game or two then your machine in mind check out what they need and then look to buy what they need or slightly above.

EDIT :: Ease of reading.

The usual suspects are:
any Radon R9 (270X or 280X); GTX 960.
Or if a little more power: R9 290; GTX 970

for your psu...should be enough if you don't run more equipment.
but remember: a new card can boost your pc; but only if the cpu isn't to old ;-)

edit:
if you are only looking for a little boost.....gtx 750 TI (or for less money GTX 650 TI)

Not a bad suggestion, but I don't have a specific game in mind atm. I was looking for possible upgrades that would be compatible with my pc. I'm fairly new to updating the inner workings of my tower, so I'm clueless as to what would be a decent upgrade from what I have that would keep me under or right around $200 Thank you I was looking for some options. now my cpu is Intel Pentium Dual E5800 3.2GHz/2MB/800Mhz Desktop CPU Processor LGA 775 SLGTG and I only use my pc for playing games, so I won't have anything else hooked up to it

I've been considering starting over with a new pc, but ebay seems risky. I wouldn't know what was legit, or not. Thank you for offering up some different options for me. I appreciate it. =)

If you go the EBay route, there are mass sellers of PCs out there. Those who have a lot of transactions, then read their feedback. Should be obvious if they are legit and willing to pony up if there is a shipping issue.

Like RWarehall said, look for someone with a good rep and a shop.
And if there is something interesting, well note it down and check other sellers.
Check the components of the pc!!!
There are reviews for nearly everything. Google or bing are your best friends ;-)
Don't buy from private persons ....or better said, don't buy a used pc (or any other electronic device).

I'm going to search around on Ebay, and scout out some pcs, and sellers to see what I can come up with. Thank you guys again for the advice. =)