Well, this is my first playthrough, so I will hopefully be more efficient next time.
Which dragon skills yield more experience? I don't know anything about that.
Also, something I observed looking back through my first game is just how fast the dragon progressed up to, say, level 25, leaving Amelie far behind in level (up to 10 levels, I'd say). Then after level 25, Amelie began to catch up, and after the late 30s she overcame the dragon. I don't know if this is one of the game mechanics or a consequence of my own choices, or a combination of both, but I found it a bit puzzling.