Upgrading to a Video Card.. Have Intel 82845g Chipset?

I have a 5 year old Gateway 500se... I just put 1 gig of PC2700 Kingston memory into it... it has a p4 2.0 GHZ and all i want to do is play World of Warcraft on it... with a descent framrate. I barely plays it at 14 fps. It has no agp or pci expres slot... only pci. How high can i go as in Video Cards... DDR... DDR2.... 512 mb.... 1 gb... Can I put whatever i want in there as long as it's PCI?