How much should I spend on a credit card with a 500 dollar limit?

Well, I'm 18 and just got approved for my first credit card. I went through my credit union and got a 500 dollar limit on a 12.111 apr rate. Just wanted to know how much I should spend to build my credit. I know that if you spend to little it can actually hurt your credit but I'm not looking to spend a couple of hundred each month. I'm looking just to spend the right amount and pay it off in full. Should I be looking at about 50-100$?