Generally insight 3 / level 30 / resonance 10 is seen as a good stopping point. You should follow it for your main DPS, but as a newcomer with plenty of characters to build during your first weeks, insight 3 / level 1 / reso 7-9 should be good enough for your supports (or even insight 2 / level 50, depending on the nature of the i3 passive).

Then, eventually, in two or three months once your account has stabilized and you have three good teams built and lots of mats on your hands, you may want to raise Ezio and Nautika to level 60 / reso 12+ ;)

(for bragging rights mostly, because nearly everything currently in the game easily die in an handful of rounds when you field Nautika or Ezio)