I mean... I've practically done everything by now, I've:

Beaten the game
Made my team L100
Filled the Regional Dex
Filled the National Dex
Gotten all the Y megastones plus Blazikenite
Achieved Grand Duchess on Battle Mansion
Created a shiny 6IV doppleganger trophy version of my team
Gotten my 3 favorite legendaries

...what else is there to do?

Right now I kinda miss the casino, so I could waste all my money on something fun...

...Any ideas?