Junction some heavy stuff for Strength, Vitality and Spirit.
Don´t mind too much about HP, I think Vitality and Spirit is much more important.
Give as many chars as possible stuff like Str+60% and the like as well.

Also, USE AURA STONES!
It´s pretty interesting that you can get them in the beginning of the game, really.
I´m going to the Timber mission right now and I´ve already got the Aura Stones.
You can refine them in Tool-RF from Steel Pipes, Fury Fragments and Hypno Crowns.