I love thos set ita gorgeous and I understand you need momey BUT gacha is not the way to do it, its the same as loot boxes and it's very predatory, the fact they "retire" will cause fomo causing people suceptible to this stuff to llikely succumb and spend money only to gamble it away missing out on the item they need, if you're going to charge money for premium items DON'T make it a gamble.
I had to stop playing mobile games all together due to this I spent hundreds of my money on games and came to regret it later as I have no disposible income. I was lucky my mum helped me stop but others don't have that luxury.

If yous care for your playerbase yous won't keep real world currency gambling, atleast thats my thought on the matter