>>532253967
No.

Rewards first, THEN stars. That's maximum efficiency. If you go stars first you lose some potential currency. That being said, this specific event is unique. Go for stars first at least up until you finish stage 9.

Why?

Because even with a maxed out team, they designed these stages so fucking badly that it's always rather difficult to get the "fast clear" task achievement. This event is, far as I remember, the only one with this issue.

Use "auto" formation to get max rewards for stages 10, 11, and 12.
Use the auto formation from stage 12 afterward on stages 10 and 11 to improve your point drops from those stages.