I have no idea what I'm doing. Someone please help me
What exactly are you struggling with?
I just dont know what I'm supposed to do. I have my full roster at level 20 but they don't do much damage still
Well the strength of your characters doesn't only come from their levels, it's a combination of everything.Basically, farm and upgrade artifacts, inhance their talents, upgrade their weapons and ascend your characters once you collected the mats and met the Adventure Rank requirement.Tbh, level 20 isn't even high. Not for Adventure Rank and most definitely not for characters, so if you feel like they're lacking in strength take a look at them and see what you can improve.
another important sidenote would be that, depending on your team constellation, Elemental reactions could be the key to victory, since combining elements can cause A LOT more damage than just hitting them with your weapons.
second sidenote, when you get a dublicate of a weapon you already have, you can go to the weapon's enhancement screen, select "refine" and use the duplicates to strengthen the effect of the weapon.Don't get blinded by rarity, a 3-Star weapon in the right characters hands can be just as powerful as a 4-star weapon