Well most of the stuff I have done are concentrated around Moon City (logically, since it is the largest city), especially the renowned, humogous and (in)famous Moon Academy.
Secondary focuses of what has been up until now are the Assassins, stealthy killers for hire which kill without leaving a trace, the Priest-Protectors, a order of librarians which handle & protect knowledge almost to the point of it being a religion, the Mages, the criminal organizations of Moon City's suburbs.
Really anything can be used so say your tastes, be it school life in the industial center of Moon City, over building a railway trough the Great Desert to the nomads of the Snowlands facing a flood of expeditons from Aerethia.
I will enjoy any type of a Trip to Aerethia, and will make sure you do the same.