People always seem to buy tiered cakes at school auctions. Just make a 2 tiered circle or heart shaped cake. Ice it and decorate with flowers (real or icing) and I bet it would be the star of the White Elephant sale.
If you don't have tiered pans, make a cake in a 13x9 pan, cut it in 1/2 and trim the other 1/2 to make a tier. Nothing wrong with a square tier. Or 2 round pans...whatever.
I have a football pan (from Michaels or Walmart?) and decorate it with the little stars for football parties. I always cut it in 1/2 and ice the middle section, too. Otherwise it's too much cake for the icing. My point being that the pans are really cheap.