This is a book of free info on how to build a surfboard
http://www.surfersteve.com/introduction.htm
and
www.foamez.com has almost everything you need
I have thought about this too:
-there are 2 main options for core - polyurethane (PU) or polystyrene (PS)
-there are 2 main options for resin - polyester (cheaper) or epoxy (5 times as expensive but much stronger)
Note that PS can only be used with epoxy
Blank cores can be bought for both PU or PS but...
Polystyrene can be bought at a hardware store (insulation) and XPS is very manageable for shaping compared to EPS
Creating a core for PU would be a lot more work and includes a balsa stringer if you use polyester
For fiberglass: shortboards use a 4 oz/yd^2 plain weave e-glass (cheaper) or s-glass (more expensive but stronger) with 2 layers on top and one on bottom, which would be really weak for wakesurfing. For extra strength I would use a heavier glass and put at least 3-4 layers on top and 3 layers on bottom double wrapping all the edges, since weight is not a huge issue
This is the cheapest and easiest option:
Buy a short fish polyurethane foam blank and shape it to your dimensions
Buy polyester resin and extra layers of e-glass
Go with a twin fin or quad fin set up so you don't have to cut through the stringer