Do I need to have real money on my starbucks card in order to get stars?

I just added an electronic card on my iphone and i want to use it for reward stars. Can i just use the card with no balance and pay with cash and still get the stars or do i really need to transfer money onto the card to use it to get the stars?>
please help i really want the gold membership thingy

My wife always has them load the money on her card, then charge it each time she goes to Starbucks.