Currently, the only limit to how high you may train your skill, is how high a trainer of that skill will teach you the theoritical knowledge part of each skill.
Magic ways are no different. Each way has it's own skill, and each much be trained as such. Exception being that higher power spells require higher ranks in that particular way. For example, if a spell is a rank 2 spell, you would need 20 in that skill before you could cast it.
