Just flick the spinner (this game is very solid. It's going to last. Nothing irritates me more than a flimsy spinner.) and take what it tells you. A big tier, some icing, a topper - it doesn't matter, they all look great. And make your cake.
Once its finished, measure the cake and collect some rosettes. After about fifteen minutes, you have a winner. And honestly, its one of those rare games where kids enjoy the playing enough so winning doesn't really matter. For ages three to six or seven.