I pretty much agree with the Cap'n.

Go with PGL for a bit to get Second Wind II/Featherfoot II at R42, then rank GLA up to R36 to get Sentinel at least and MRD all the way up to R50 for Bloodbath II/Defender II/Foresight II. In whatever order you feel comfortable with!

MRD is my main so I have that down. The other two classes and getting those ranks are what I'm working on myself right now. Seems like the best course of action for skill collecting!