I've been playing since Day 1 tho I have missed a few days here and there I have managed to get a copy of each and every event girl at the time of the events. I just hit 727 days login if that helps get a sense for how long that is. For me right now it's all about the blooms and Life Crystals, those petals are the only thing holding me back right now.

If any new players read this:

Get 6* Dendrobium and get 5* Cymbidium. level them up . Add any girl you get to fill team.
This is your daily sweeper team that will beat 99% of what is there.

Farm the reprint events and get all the girls with 1.2 Skill activation.
Get Kerria, level her, and put those girls on the team.
This will beat anything.

Good Luck.

Dendrobium is amazing for the whale missions since all the enemies on the ultimate stages hit like a truck. Dont just use her for Hit stages, use her on your first squad for every attribute mission.