I honestly don't know much about florists at this point, but with regards to the "what kind" and "how much" you could consider going to a flower mart to see what you like and the ballpark costs of these flowers (keep in mind a florist will build
in a cost for their labor and creativity).
Not sure if you're in the Bay Area, but you could check out the SF flower mart for inspiration.
http://www.sfflmart.com/
You can also take a look at Sam's Club to get an idea of what wholesale prices look like.
http://www.samsclub.com/sams/shop/category.jsp?categoryId=1240