I've always purchased our dresses at home and brought them with us. Actually the Cinderella dress I got a few years ago was so cute that we had many people at the Magic Kingdom ask us where we found it. This year I found a Snow White dress on clearance at a local store after Halloween. It's beautiful, not the Disney dress, but has a homemade look and an overlay sparkle skirt - very cute. I also found a Belle dress on clearance at a toy store that we will be bringing for youngest DD this year.
I'd say try to find a dress at home and save the money to put towards the BBB and let her buy all the shoes and accessories.
But if it's a headache to find a suitable dress at home, just go for the Disney dress while you're there and let the princess splurge!
