Alternately titled "How to make magic versatile and also incredibly obnoxious to GM".
So far I have a number of different schools of magic based on the rules, for how it all works in the Wastes.
Spell-based magic: This is the stock standard magic system for GURPS, equivalent to what's found in fiction such as the Harry Potter series. You don't learn the deeper workings of magic, you just learn directly how to do whatever it is. It isn't versatile, but it's relatively easy to learn what you want to do, and even your average non-mage in high mana areas might pick up a few simple spells to make their lives easier. Fairly easy to learn, either in a magic academy or just out of "learn magic" books.
Theory of Magic: This encompasses schools of magic that study the actual root workings of magic. Instead of learning a set order of words and motions that will result in X, you learn the ebb and flow of magic and how to manipulate it. Roughly standard rules apply for ritual magic, runic magic, and syntactic magic, all work for this particular style. Many options for achieving the same effect, manipulation of magical energies.
Wild Magic: This one's a bit tricky, and will be hard on the GM. It's based on wild magic out of a series of books, where anyone can be a wild mage. It's an intrinsic thing, and you don't really study it, you just HAVE it. It's a bargain-based system, but for minor things you can just power it yourself or off powerstones. The best example comes from early in the first book, when the protagonist goes out when he isn't supposed to and happens to lose his key. He invokes the wild magic, and agrees to the price: The wild magic takes him over, runs him halfway across town, and he meets a little servant girl who's kitten is stuck in the tree. If the kitten is found, it'll be killed and the girl will be punished. He climbs the tree, and lo and behold, there's his key in a nearby magpie's nest. Wild magic is ALWAYS good aligned, although someone with another power source (demons, etc) can convert it over into working like ritual magic (it no longer functions as Wild Magic, and they can never use the bargain system to power spells again).
Blood Magic: Not a school of magic in and of itself, blood magic uses the Sacrifice rules in Thaumatology. Pain, suffering, and death release power usable to mages, but it carries with it a taint. Prolonged torture can release as much energy as killing outright, but leaves a VERY noticeable taint of sadism. A necromancer will feel like they've been making gore angels, while a battle mage who casts from the energy available on the battlefield may just FEEL like a battlefield, while a professional assassin who kills instantly and painlessly will have a cold, clinical, sterilized feel of magical taint. A blood mage who casts from himself while specializing in blood magic will avoid the -1 penalty for casting from health, and get a significant boost of energy for each point of health used over non-blood-mages.
Dance limited magic/bending: Another instance of magic available to people without a ton of IQ. This is pretty much the elementalist knack straight out of the Avatar series. I'm still working out the kinks, but it'd be tied to a martial art, and most likely limited almost exclusively to very direct magical effects. A firebender can shoot all kinds of fireballs and flame jets from their punches and kicks, but can't summon elementals or shape fire that's around. I MIGHT make other effects (summoning, etc) available with significant extra time through extensive ritual dance, still working out the details.