Hmm... A principle is not a source of magic, nor a type. It's a principle which allows magic to happen, and governs how it happens. Is that right?
Your knowledge of the principles shouldn't dictate what kind of creatures, but perhaps govern how well you work with them? For example, if you are well familiar with the Principle of light, and darkness (governing perception) and the Transposition Principle (Distance), would that make you work more easily with Archers? Would they gain levels easier, come at a lower price, etc? Creatures with a "Weaken" attack might be used more effectively by someone familiar with the Principle of Enthropy, for example.
Does that make sense?