sugestions please

I semi_purchased a 2002 civic ex (its a cross between lease and purchase) they call it a customer option plan. Anyway, im looking to make my car a little faster but I don't want to alter it so much that I have to keep it after three years. what kind of stuff can I do? How much money? ( i don't want to spend too much). The car seems like it has a little potential with a couple of quick mods. AM I right?