The different oriental styles don't seem to be that widely apart. Many seem to be down to where the weigh is, minor variations in movement vocab and posture, attitude and prop use. Given time and inclination, I think a good dancer should be able to perform a range of oriental styles very well.
Folkoric is a whole different area. I've been told there are over a hundred variations in debke alone. I've personally decided to concentrate on Egyptian folklore (cutting out debke, shikkat, Tunisian etc etc to start with). But just in Egypt there is sa`iidi (minor variations by region, big variation by sex), ghawazee (multiple styles), Bedouin (yes there are Bedouin living in Egypt) including Haggalah (ie as per Mersa Matruh), fellahi (as far as I know only info has been filtered via Reda and Firqa Kawmiyya - but it is there), Bamboutiyeh (Port Said), Nubian (many styles), tanoura and zar, then there's the old ‘awâlim style, a range of things thrown in the "beledi" basket, the brand spanking new meleya lef (multiple styles), the slightly older raqs sham’idân ... a person would have to dedicate their life to master this one country alone. And then you see people offering "all styles" - grr
