I started by disecting military baggage its cheap and built to carry weight and be comfortable and when you done you have a pile of 14oz duck or cordura and strapping to turn into a messenger bag backpack pannier what ever you feel like doing

I will also suggest getting an older home machine with a strong motor if you don't already have one older singers with .8~1 amp motors have neought gusto to go throught triple folded seams on thick material newer machins have weaker motors and plactic drive peices if you must buy a new machine singer just came out with a consumer commercial series with strong motors and all metal drive peices
also I would say get some thick needles as well 16 and 18 size work great for most things I hope this gets you going in the right direction