I'd suggest a small tweak in the report of
@Chihiro in #19.
For the grouping change the settings (untick) "Summary rows below details".
It is not a big deal, I simply find it more intuitive that a "menu" drops open downwards.
some top of mind things that popped up...
This report contains so much info, the information drowns itself. "Whacking your brain..." indeed. I believe for a data analyst this is a great report though. You might find suggestions that some products are not successful. Shirts and swimming clothes might not be selling well, but perhaps you had 2 great summers or 2 warm seasons in a row, so people did not need to buy again or sales was more spread? Is there a correlation between visits and sales? You might be having more visits, but lesser or declining sales. => great website, but lousy products? Would you have loyal consumers (if that data is at hand)?
Those are the things a data cruncher can present to decision makers.
In the line of #15...
I'm not a great fan of simply comparing this year vs last year. At least a trend over several years might show a different story. As in "we did better then last year" versus "yes, we do better then last year, but in the overall trend our sales is slowing down".
MALE SEASONAL APPAREL only contains 1 sub item, you might group is in another way, like add it to MALE OTHER.