Main thing to remember is that if you sort by Total Power you will get a lot of high HP but low ATK girls in your teams.
"Total Power" is just HP, ATK and DEF added together when it really should be something closer to (HP+ATKx2+DEFx3).

Another useful thing is putting girls with low HP high ATK in the same squad.
High HP low ATK girls take time to do damage and should be placed together, otherwise the low HP high ATK girls will die before the enemy.

Another pro tip is seeing what skills / passives the girls have and working those together.
As a new player you won't see many of them having a great effect yet but eventually the game is all about them.
For example placing all your +ATK girls together works really well, as does all your +DEF girls.
Some girls have special skills that happen at certain times (Turn 3 skill girls and Turn 1 girls i'm looking at you), placing them all on the same team really helps.

Bottom line, don't be afraid to play around with your teams till you find something that works for you. Each player gets different girls from Gatcha so it's different for everyone.