Hi Justin,

Firstly congrats to your success, Cheers!

For developing a good list would suggest upping your engagement, why not start with the people who bought your offer, (Get a survey done may be just talk to them in structured manner in a way suits you) May look at expanding the existing site or a new one and go right out talking about yourself, your product and genuine benefit it can bring to other people.(Go beyond the sales page) In a nutshell expand and offer something in return for subscription.