First, is it important to apply epoxy to the bare wood before applying and filling the fiberglass weave

You will find different opinions on this - some folks do, some don't. If you haven't much experience with epoxy, it's probably easier to pre-coat with epoxy. I'm assuming you are talking about a 'seal coat' of epoxy which is allowed to harden before laying glass on the surface. This coat shouldn't take much epoxy- be quite aggressive with squeegee (or selected implement) when spreading the epoxy. You definitely aren't looking for a glossy surface (& drips) with the seal coat.

does that just add weight and wetting out the fiberglass would be good enough?

There's probably not much difference in weight - the idea of the seal coat is that it could reduce weight overall, but I haven't found that it seems to make much difference for me. I've epoxy/glassed quite a lot, though, so I think I can keep good control of the epoxy amount if wetting out over dry wood.

Also, how much time should be allowed between the first coat of epoxy and subsequent filler coats?

This depends on the temperature and the hardener you use (and brand of epoxy-check the manufacturer's info). I like to try to add filler coats as soon as I can. If I let the epoxy cure (overnight in warm weather or more) then I usually wash the surface as I've had some problems with amine blush in the past.