>>532134086
>do I ever want multi color teams?
No, though there will be situations where a character trumps colours.
Iroha is blue, but she's so strong for maps that she can definitely be used in red and frankly will do fine in yellow despite that being her worst matchup.
sHanako is also just good against everything.
Likewise newfags often struggled for blue AOE damage, so using a yellow was servicable.
>do I always want a tank and healer?
Probably. There are some dps like Mika that are tanky enough you can use them as the tank with a healer, and sometimes you can do a map without a healer if your tank is good enough, but it's easier to just run a tank and healer and then experiment with dropping them if you need the dps.

Stop spreading your resources thin too - leveling up every student is going to bankrupt you before long.

Circled characters I'd consider most useful, might have missed a few.
sHanako + Iroha should dumpster campaign though, split them up when you start needing to field 2 teams.
sHanako benefits from having cheap EX's on her team to cycle back to her / get multi use, so bear that in mind when putting in your filler.