I'd farm the cheapest chapter 11 stam stage for 80 stam bonuses if you need life crystals and manyus. Leveling gets expensive so farm the most potent manyus you can get

Event 80 stam stages give the best event currency for knocking out the event lists, so spam the highest phase 2 stage you can for that (does not work for reissued events)

There's also whaleship bonus stages if you can handle anything from it's chapter 11 onward. Not sure what the best one per stam is, but go for it if farming sun medals