The around $50 means it will not be a good card for gaming.
I am assuming you mean PCI x16 slot. If you mentioned the make and model number I could be sure.
PCI x16 version 2 is the latest standard and is also compatible with tho older PCI x16 version 1 slots.
Looking at newegg.com for 5 star rated with at least 10 reviews I think these 3 are the best.
Please note the MINIMUM watts and the MINIMUM 12 volt amps required. If your existing power supply is rated less than this you will also need to upgrade your power supply, which will add another $50 or so to your total cost.
ASUS EN9600GSO/DI/512MD3/V2 GeForce 9600 GSO 512MB
$39.99 after $20 mail in rebate
Power Connector 6 Pin required, 450 Watt power supply and 26 Amps available on the 12 volts rails.
Galaxy 95TFE8HUXEXX GeForce 9500 GT 512MB
$39.99 after $20 mail in rebate
Minimum 350W or greater system power supply with a minimum 12V current rating of 18A)
GIGABYTE GV-R467ZL-1GI Radeon HD 4670 1GB
$64.99 after $10 mail in rebate
400 Watt or greater power supply
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=2010380048+1069633099+4026&QksAutoSuggestion=&ShowDeactivatedMark=False&Configurator=&Subcategory=48&description=&Ntk=&CFG=&SpeTabStoreType=&srchInDesc=
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=2010380048%201069633099%204025&bop=And&ShowDeactivatedMark=False&ActiveSearchResult=True&Order=RATING
Graphic card performance Charts
http://www.tomshardware.com/charts/