What should I buy the girl I like for valentines day?

There's a girl that I really like, and I want to buy her something for valentines day. We get along really well, flirt a little, and honestly I think she likes me too. I really want to give her something special, but I don't want to give her anything that's too intense. I also want her present to be small so I can fit it in my backpack, as to not be lugging it around everywhere I go in school. Chocolates seemed like a good idea, but are they too serious of a gift that should be reserved for couples? If not, is it cheap to buy them from the pharmacy?