For a good introduction to a variety of styles of music (including classical, folkloric, pop, club, and fusion), the Bellydance Superstars CDs are a good place to start, and many are available as MP3s/on iTunes. I personally have volumes 1, 3, 4, 5, & 7. These CDs vary quite a bit, and some of the volumes are mostly club/techno type songs, so read the reviews and listen to the sound samples to see if the volume you're looking at has the sound you enjoy.
For compilations of classics that you can't go wrong with any of the Masters of Bellydance series (volumes 1, 2, and 3), "10 songs every bellydancer should know" is great, but has a lot of the same versions of the same songs as the Master's series, and anything produced by Jalilah. Hossam Ramzy also has several good CDs, I enjoy Faddah and Ruby, but I honestly go through phases where the synthesized instruments get to me.
One note about Jalilah's CDs: Volume 4 is a rhythms CD. This is great for learning rhythms, but the format of this particular CD, where she plays just the rhythm and then an excerpt from a song where that rhythm is used (in Egyptian music, especially for dance, the rhythm will change up every so often, to keep things interesting) might not be too easy to practice to. Other CDs that will give you long tracks of a basic rhythm played include these by Mary Ellen Donald, Drum Songs for Dancers by the late Uncle Mafufo, and Dr. George Sawa's Egyptian Music Appreciation set (middle of the page) which is certainly an investment. Any of these tracks are great if you're getting frustrated with the rhythm changes in a full song while you're trying to drill, but they can get boring if you are just drilling to them and not listening to anything else. Pop music can hit a nice middle ground, of not having too much rhythm change (good for long practice) but having words and melody to keep you engaged and having fun.
If you're looking for things on Spotify: They do in fact have "10 songs every bellydancer should know", as well as great tracks from "The Art of Bellydance: Suhaila's Supreme Selections", a few of Jalilah's albums, "The Queen of Balady" album from Fatme Serhan, "Casbah Bellydance" by the Salatin al Tarab Orchestra, and much more. Try making a channel from any of these and see where you go!
Pandora mostly had tribal fusion music when I tried it a few years ago, such as Pentaphobe and Beats Antique. This might have changed since the last time I was on there.
Of course just because I haven't mentioned it here doesn't mean it's not good! There really is an overwhelming amount of music, of varying quality, out there these days, thanks to dancers who support the musicians making the music, and you can also practice to whatever you enjoy (I've been turning on Uptown Funk when I get feeling stuck ^_~). The more Middle Eastern music you listen to, the more you'll develop an ear for it and be able to feel the transitions and flow of it letting you translate the music into motion and get swept away, which is ultimately what dancing is all about. When starting your practice put on a song that doesn't have too many changes. As your library grows I recommend making playlists: a playlist of fast songs, of slow songs, of Egyptian, Of Lebanese, etc. This will let you put on the right music for your practice at a click, and focus on your practice until it's time to cool down.