From what we saw from luke until RotJ to what we see with Rey in TFA, Rey is already at least as powerfull as Luke with no jedi training.
She's the "Rey of Light" (side) in the prophecy. That was the only interesting story point for me in TFA besides wondering what was going on politically. Ironic since the prequels were mostly about the politics and boring a lot of the time. What is Rey's story? Is she Han and Leia's secret kid that Han didn't know about? See the whole Falcon flying scene. Luke's kid? Do I really even care? At this stage, not really.