Level 15 TMG

[Cikala]

You could also start getting into dungeons. They give good exp and really good gear for your level. Not as fast as FATE parties, but still.

At level 15, I'd dare say doing the three starting dungeons is just as fast if not faster than fates. Assuming of course you don't have to wait forever for a DF queue. Each dungeon should give you just over one level when doing it at the first level available, due to the exp chains you can get, and usually takes no more than a half hour each.