Hey, the 4650 is not horrible, but for 80 bucks....grab this little guy.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814161252
70 bucks with a 10 dollar mail in rebate.
And don't listen to troll. He's a newb. I'm like the OP, I don't always have a lot to spend on hardware, though I love computers and games. I've actually got my Bachelor's for IT, and have my apple certification, but with a family and all, just don't have the time for games as much. But according to reviews, the 4670 is nearly as good as a 9600gt. Which is the card I've got, and it honestly does good. If you run lower resolution say at 1280x800. Then you should be fine, and be able to put on a little eye candy, don't expect too much from the card though.
As far as 512 ddr3 vs 1 gb ddr2, the ddr3 is better. The ddr2 is slower, and you'd only need 1 gb when running high resolution or too much eye candy, which by that time, these cards would be choking because they aren't made for that. Personally, I'd grab the 4670 and be happy for a while, as I said, just don't expect too much from the card.