Tory, Hi and welcome to the Toilet Teaching board.
In my opinion, for potty chairs/seats, I would wait until your DD shows interest, and then allow her to pick out the one she wants, along with underwear. Also there are many books/dvds for children, I opinion is to read and watch the dvds together when your DD is showing interest. Many children start showing interest around 16-24 months. Of course their is also the decision to make of what method(s) you may want to try. I hope that helps.
I totally agree with Christina