Please note the following, Ms. Jessi,
The GP2X does not take DS cards, they are pulling your leg.
You will need an SD card, choose whichever size you can afford, and before buying, ask us if that brand and model of card is known to work (some are incompatible, the GP2X is a little picky). You should be able to get one at the place you buy the GP2X.
You may also need a card reader, so that you can easily copy files from your computer to the card. You should be able to get one at the place you buy the GP2X. Remember, you get the games and programs by downloading the from the internet, and copying them from your computer to your SD card.
Sorry about all the spamming, joking, and topic-stealing. The geeks are just a bit uptight around less knowledgable people. They aren't usually like this. If you are who you say you are, and you really want a GP2X, then we well come to respect you more later on.