I don't know what everyone's rush is with trying to build a credit line, especially with a credit card. Especially dumb kids who over-spend and can't pay it off and end up in debt up to their grandchildren's eyes. Anyway...
Just keep track of what you buy and be damn sure to pay everything off on time. You have $1000 limit per each month? I'd only put $250 on the card, max, but that's just me...Hell, I don't think I'd spend $250 a month at all, but that's your call.
Best of luck.