I've been to the desert. I have the map, I did a few errands in Dusk, and the nearby Dragadune castle, but not much else.
If you're looking for experience, there's a very useful place to visit in Castle Dragadune. In fact, I think one of the lords will quest you to find it, so if you haven't gotten that quest yet, it's worth seeking out. My memory is that you get the quest from one of the lords near Erliquin... not Hacker, the other one (forget his name at the moment). His quests generally ask you to find various places in the world.
I think I'm gonna advance on the main quest. My progress in that one is that I just obtained the Ruby Whistle.
A good idea also, although I'm not sure you're high enough level to fully tackle the next step. But it would be a good place to get experience and loot... get in a few fights, then retreat to save, etc. Try it out and see how you fare! I might be biased as I was higher level when I tried it so I was getting tougher enemies in the random encounters. You might be fine.