Up to you, really. Although since you asked, I'll list all the available crew roles again from most important (top) to least important (bottom)

Doctor
Shipwright
Engineer
Navigator
Cook
Helmsman
Entertainer
Swabbie
Enforcer

The Swabbies and the Enforcers in particular could be apped for multiple times if you guys [i]really[/i] wanted to do so, but I'm imagining rather reserve the more unique roles while they're still available. I'll update the list of reservations on the 0th post as you make them.