You'll be able to switch paths at some point, so you're not necessarily locked into the one you first pick. If memory serves, there's an option you can eventually unlock with mementos that allows you to choose what stance you start with in each battle.
Sage/Coward is probably the easiest, lowest effort stance build. Their buffs are mostly about damage% increases, which I think is just generally fine for casual play. DPS ceiling is probably the lowest.
Warrior/Brave/Hero is like a tanky stance, a bunch of resistances, and you've got a big burst but it takes some time to build. DPS ceiling is pretty high. But, sometimes it can be tricky to set up your burst, and if you are interrupted by something like a forced stance change, that really hurts for this stance that doesn't do much "damage" outside of the burst.
Lunatic/Slave is a bit wonky. They've got a buff that increases both their crit chance and the enemy's, and they take damage from using some of their own abilities. They have the highest base damage for their non-burst abilities, and get the highest critical damage bonus, all of which means their DPS ceiling is the highest (it's possible the Love stance has higher DPS still, but that's a scripted stance).