Last night I pulled out and dusted off my Stephan Wremble book, getting gypsy jazz, and unearthed a great nugget - 9th arpeggios ! I was always reluctant to work on the 9ths and 13ths arps because it was just too much info what with all the other arps/licks/phrases I was learning...
BUT - Last night I tried them, and WOW they're pretty freaking cool. Basically they play similarly to pentatonic scales. They're all 2 notes per string (the "closed" arpeggios), and can be really easy to learn and groove on with a nice swing because they're easy on your right hand gypsy picking.
Once again I discover that you can learn pre-created phrases, which can be great, But it you want to learn the foundation of most cool licks and phrases out there, things like the harmonic (and melodic) minor scale, whole tone scale, enclosures, and 7th/9th/13th arps are the way to go.