Also the decaying crystals will make players want to hunt down the better crystals that drop. Since they do not decay and can be ‘eaten’ for the consumed crystal effect as well as the experience they give.
this would actaulyl be a problem, not a benefit. if people can hunt for better crystals than they can buy, they won't waste money on crafted crystals. the crafted crystals will have ot be every bit as good as the dropped ones, otherwise people won't spend for them, money is hard enough to come by as it is, we don't need to be wasting it on crystals that are pale immitations of what we can get hunting.
as far as resources go... make 'em like cyrstalline lattice. hell, here's an idea, assume maximum efficiency:
requirements for one blank crystal:
5 tr-cut gem
5 primal essence
one may then take the blank crystal, and apply to it the same resources that would be needed to tech a piece of equipment with the same properties.
so final requirements for a fully-working crystal (again, assuming maximum eficiency) would be thus:
5 tr-cut gem
5 primal essence
5 essence orbs
1 <tech item>
1 <tech item>
this would allow a dragon to craft a crystal with the desired properties, but would make it take real effort. the base resources themseles would not be an overly large obstacle, but would still require effort, and the tech resources would require some ammount of hunting, so even if one makes silos full of the craftable resources, one could not produce a torrent of crystals.
obviously this would mean that either experience per level would have ot be lower than most schools, or experience gained per crystal high, or both. otherwise it would take far too long to level.