at the moment im lvling my ijn bb crew first to fuso lvl
but then ill focus on my ijn cv crew
try to get +12 in fighter and bomber stat if you cant get that get +11 works also good with experts and vets
personally go for 4 fighters and 4 divebombers, even though torpedo bombers are usefull the high tier bbs have so much bulge you wont do much against, km medics wont work so dont bother with that get 1 seaman with +12 in fighter stat or buy a elite lvl 12 fighter pilot and class it seaman works even better i heard
for gunners i suggest to keep them armenant sailors as you gonna need AA at higher lvls when you have reached a cv that can hold guns use PHH or HH to attack subs that are coming your way/ class your armenant sailors at lvl 89 into chief dp gunners that will work the best
hope i said enought that can help you good luck