Very few classes/job draw power from outside sources to fuel their abilities. You can draw extra power from outside sources; Estinien and the eye, BLMs of old using voidsent as living batteries, etc, but it's not required.

With the exception of conjury (which borrows aether from nature elementals), everything is powered by the user's own personal aether. Warriors and monks use aether to strengthen their bodies to hit things harder, dragoons use it to jump super high, and so on. Even the purely physical abilities are actually magic underneath.