Thank you for all the help provided, guys.

Looks like I did better on the whale now since I could clear the first two stages of Mission 1 (Well, my strongest girls are slice after all), but since the next one requires a 800,000 power level and I'm only at 750,000 I think I should focus on leveling the dozens of underleveled girls I have.

On that topic, I usually tend to neglect most event girls and leave them with no equipment. From what you guys said, equipment seems to be very important on whaleship. Should I fully equip all my girls or only bother with that if it is the special equips? (I don't have that many). I didn't even bought the dressbloom and skillbloom of the new girl and went straight for the equipment and atk amps. Guess I should correct that, right?
Also, If equipment is so important now should I prioritize those upgrade material before lvl100 manyu and amps?

And sorry for the noob question, but what mission is W1-5?