Yeah that's pretty much what I plan to do if mine gets banned. Just buy an account with most characters. I bought an Epic 7 account beginning of this year
and now im only missing 2 characters, which are ML5's. Tho I still had to do abit of whaling to get that far.
I know its dumb but I wish there was a unit injector to play around with team builds, I also get shafted pretty hard I'm on like 15th multi with no 5 star
30 extra stamina from daily quests, then if you look at othe events there's lots of quests from Training and if you repeat those x5, x10, 50 times and so on, they give you extra stamina or bottles.
Also level up the food shops in the city to increase bonding faster. Most quests from bonding give you stamina bottles. I used like 100+ bottles and now I saved up 157 again. Probably keeping them for next event tho.