Originally Posted by
Iscah
Do you specifically want to level up the NPCs for the sake of it (titles/completionism/etc), or do you just want to have them levelled so you can go into higher dungeons and gain EXP for yourself?
If you want to level them, use Trusts.
If you're doing it just to level yourself, you don't need to bother with levelling trusts at all. Use Duty Support to freely enter any dungeon that has NPC support.
And unless they've changed it, Duty Support mode does drop gear and other loot – although I think it tends to have one gear piece per chest where a normal party would get two.