Just really think about your leveling your characters along with the gear you have...it's the most important part.
Commit to your role.
Every class is insanely powerful if built right. Also just experiment with different spells and stuff. Some of the spells that seem useless are some of the most powerful, like Sanctuary for example.
I've been playing a build where I just throw people and items at people and I'm destroying enemies. I use Misty Step get as high as I can and throw things like Heavy Treasure chests at enemies and I carry dead bodies in my inventory. Lol.
Thief #1 "Hey, look, I lifted this pouch from XXL over there, wanna see whats in it?"
Thief #2 "Oye, that's a bag of holding, there could be ANYTHING in there. Quick let's dump it out over this little hill!"
Thief #1 "By the GODS, its a slaughter house! There are women....kids...dead! What kind of monster has this bag?"
Thief #2 "Eh, they's all orcs and goblins and stuff, nothing of importance!"
Thief #1 "True, true, guess we knows what happened to those 3 villages of hobgoblins across the river...."