My advice is to not push ahead to 11 until every single team is good and ready with equipments and affection levels. Otherwise you push ahead to 11 unprepared and realize it was a complete sham and a waste of time.

There is no single way to play the game. I'm sure some bloke is going to roll out "most efficient and fastest way to grind" FAQ, but those are really only for players with multiple-accounts, seeking to offload extras for a quick payday (illegal things are always happening) Getting 3 medals is not necessary, but yet they're essential for players who are complete freeters (not a single IRL dime in the cash shop)

There's strategy and composition involved in events, but again, since they're completely voluntary, don't feel pressured by it.