Skill gems for Storm mages

I was looking for skill gem recommendations for my storm mages.

I am currently using

Feeding frenzy
Arcane tempo
Muster
Lightning mastery
Minion Mastery

I have 521 spirit running 12 storm mages with 5 other persistant minion types.
I am only using them for there basic attack (635-12018) which chains 5 times.

Was wondering if there are any good gems I have missed that could use to boost the damage further.