How do I know what kind of Video Card I should get for my PC?

You need to get one that fits the mother board slot, pci expressx16 slots look like this |====|==========================| not this |=========================|=====|. Newegg has best prices and they are easy to install at home. Buy one that is priced 60 to 80 dollars at Newegg, anything more and your pc won't keep up with it as the extra video power will be wasted. You really need a newer pc if you can afford one. Even a $400 desktop would be way faster than your old one.