Gypsy jazz can be tough with all of the endless experimentation. I found a great tool that enables you to make a quick chart of a useful arpeggio for any arrangement that you happen to be working on. Nearly all arpeggios can be derived within this one simple tool.
Nothing has ever made jazz easier. Here is a great example of a chart that this tool can create.

The pentatonic minor scale sits in the first five positions on the circle of fifths (going clockwise) and has an eclectic sound. It creates a form of symmetry, although its not technically symmetrical like the diminished scale, and therefore can be used in special situations.
I generally try to avoid using this scale for fear of sounding too much like a blues or bluegrass player, but I am starting to see situations where it can sound ok when playing gypsy jazz.
For example, in the key of A major, since the relative minor is F# we can use the F# pentatonic minor scale, the A major scale, or the F# minor scale, among others. Listen to this scale as you play and while you should use the natural minor or harmonic minor more often, you may eventually feel that this scale will sound ok over a gypsy tune.

I had an observation about the circle of the fifths, while studying Romanes “L’Esprit Manouche lesson book. In the key of A (from page 19) Romane writes a progression (constructed completely from the minor harmonic scale in A) as such:

I   ii   iii   IV   V   vi   vii
Am  Bdim C+    Dm   E   F    G#dim
Am7M Bm7b5 C7M#5 Dm7 E7 F7M G#dim7
                     E7b9

I am not sure what to think of this because I am just learning the circle of fifths. Compared to the generic jazz progression below (from page 70), it is interesting to note that this progression on page 19 has a ‘flat 3rd’ chord and a ‘double flat 7th’ chord. More importantly, when this happens, deriving from the harmonic scale, you end up with major chords in those positions.
Standard jazz progression:
I = A = maj7, maj9, maj11, maj13, or 6
ii = Bm = m7, m9, m11, m6
iii = C#m = m7
IV = D = maj7, maj9, maj13, or 6
V = E = 7, 9, 11, sus4, 13
vi = F#m = m7, m9, m11
vii = G# = m7b5
More specifically, if I use my existing knowledge of jazz circle of fifths, what sort of sound will I achieve if I alter the iii and the vi and how should I think about those two positions? What will I do with this idea?
Also, if you know anything about the “III” position (the V of vi), or the “II” position (V of ii), does this mean that in the key of A, for the III position, i use some sort of C chord instead of a Db (7 or sus4)?