Something with a low limit, no annual fee, and something you're planning on paying off at the end of every month. And if you can find one that gives you rewards, that's a perk too.
It being your first card, you'll probably experience extremely high interest rates - which is why it's important that you pay it off every month, and that your limit is low, so you aren't tempted to go overboard.
My dad has been in the financial advising business for decades, and he always preached to me - "If you don't have it in the bank when you pull out the credit card, you won't have it in the bank at the end of the month."
Make smart decisions. It will save you a lot of stress and money in the future.