How would you have done it?

Question

I am at the end of a project, and I don't have much experience, and was just wondering if the way I did things were sensible, or if there were better ways. For example, part of the program tracks orders. I made an order class, with several List type properties or classes such as pizza, sub, side, drink, etc. the pizza class has several List properties as well, for single toppings, double toppings, halves, etc. Upon completion, orders are serialized and stores in a database.

So now I have Lists that contain lists, and I was wondering if this was a mistake. How would a more experienced programmer have done things? This works, but what sort of problems am I setting myself up for?