User blog comment:Shinhwalee/Major Event Preparation Guide for Admirals (OUTDATED)/@comment-27058477-20160116121451/@comment-1870533-20160122025943

A rule of thumb is level 30 for easy, level 50 for normal, level 70 for hard.

Things get a lot more complicated with mixed levels, equipment modification levels, ship selection, ship locking, map difficulty, farming goal, etc.