How to get diamonds in endgame and the future without paying money?

With new outfits coming out every month which would probably need around 160-240 pink shards (about 20.000 - 30.000 diamonds) every time.

I'm at the point where I cleared every single quest, found almost every treasure and completed Kilos levels. Right now I have around 8000 diamonds and I get around 100-200 per day if I'm lucky. With this diamond revenue it would take me around 200 days to be able to pull one full set.

So how the heck are you supposed to get those without paying real life money?