Trouble getting the registration options to appear for membership levels

Hello there,

I'm ideally trying to use the registration process for signing up new sites on my network as defined on:
http://winkpress.com/memberhip-pluin/wpmudev-membership

Overview of process proposed
Prospective clients on payment option within sales page--> Payment is handled --> Redirects to registration page using Gravity forms to handle the multipart registration process ---> After registration they are login in to the site (or through email verification)

Does all of this make sense? It seems like a rather straight forward path but I can't seem to find the right combination of plugins to pull this off? Membership, Marketpress, Prosites.... What is your recommendation to handle this simple process of registering new sites on my network and adding new members to some form of a list?