I'll tell you what I took . . . I did the peak performance buoyancy class (and if you teach it, PLEASE make it more worthwhile than what I did). I did the deep specialty (and please, if you teach it, introduce some gas management concepts, which weren't in my class). I did part of the navigation specialty, which can be a very good one if you are diving in areas with limited visibility. And I did Rescue, which I think every diver, everywhere, should do.
My husband did the photography specialty with a very good photographer, and got a lot out of it.
Whatever specialties you get certified to do, please spend some time thinking about how you can maximize the quality for the student, instead of how to teach the minimum required and go home with your paycheck.