There seem to be two types of magic: the power that originates within and that which comes from a substance (fairy dust, potions). The former seems to be acquired by taking it away from a possessor (and so far, it seems the only way to do that is by killing). The latter type of magic seems to be learned (Rumple’s lab and books, the recipe for the sleeping spell and the dark curse) . But whether a person has to have inner magic in order to use the substance magic remains to be seen.
I’m looking forward to seeing how Cora and Regina got their powers (I suspect Regina got hers by killing Cora, then apprenticed under Rumple to learn the substance magic.) I’d. also like to see the birth and development of a fairy. And Jefferson–is his magic limited to a sole substance?
Morraine does say something about the Reul Ghorm being “the original power…bigger than anything.”