Destiny points are for modifying new playthroughs, you can't use them anywhere except when you start a new game.Do the destiny points do anything? Can't seem to find a place to spend them but it says they can be used between campaigns so I guess there's a use for them.
And what is a good party setup?
I'm kinda struggling to get anything done above novice level dungeons, I use warrior or paladin up front, cleric second, rogue/mage/noble third and ranger last.
As for the setup, almost anything can work as long as you have enough healing.
Personally I've been running Paladin, Warrior, Cleric/Cowgirl (Tomo got captured, poor girl) and whatever, Rogue works fine, because stackable DoTs are seemingly the only reason to deal with healing on the enemies team. A mage is fine too.
The most important part is to pay attention to stats. Just because you can nab a purple Veteran Cleric from the Stagecoach, doesn't mean she'll make a good cleric and the best course of action is to outright switch her to, say, a Warrior, because she's an Aggressive Brat with 20 Strength and 5 Wisdom.
For example, my aforementioned Tomo has like +200% healing power due to her "SPECIAL" stats, quirks and maxed service tattoo (the purple one). She also does literally zero damage with every possible attack. As such, I need no other healer on the team.