Beastman - All 3 sets and a board are a good starting point. This should give you a wide range of things you can do and enough tiles to build a fairly large encounter area.
After two years, my inventory of the boards is very low. I have about 24 left and once they are gone, they are gone for good. I also want to be up front and say that there are no longer plans to expand this product line, since it hasn't proven popular with distributors or made much (any) money for my little company.
I hope this helps. Please note that any orders placed through the web site will not be shipped until August 1st since I am heading to GenCon in just a few hours.
Cheers - Edward Bourelle