How can I make an easy and inexpensive Minnie Mouse costume?

Minnie Mouse usually wears a matching red dress and bow with white polka dots and yellow high heels. You may be able to find these as a thrift store. A red dress without polka dots may be usable if you can't find something that matches exactly. If you find a long dress (and are handy with a sewing machine) you can cut off excess from the bottom and use that for the bow.