Leves, FATES, Dungeons, Logs, and Behests. Or, get a group of people of the same level together and go find a place to camp mobs high enough above you all to get good xp.

Once PvP is in, who knows, maybe that will be viable. Right now, the above list is what you got.

And remember, you're not a real 50 until your support class for your job is as well.