1) Save up more money, get a new computer, and get a new, good videocard.
2) Buy your own computer, get an absolutely deplorable video card (just so it works, no games now) and then save up more money over time and get an awesome video card. If you have, say, a spare Radeon 7000 or GeForce MX400 or something like that, stick that in there for a while. However, I'm sure you'll be going PCI-Express, so you'll have to find the cheapest PCI-Express video card to run. I wouldn't spend over 30 bucks, myself, and then I'd just wait until I could get a good one. Or a motherboard with onboard video, but that'd be hard to come by.
Hope this is readable... It sounded confusing as I was typing it.