Would be cool if the gatcha machine worked similarly to the gift gatcha in Danganronpa games. Where the more gems you put in at once gives you a higher percentage of getting a figure you don't already have.
Although for that to work you would have to be able to get multiple gems per run. Maybe they could be hidden behind random interactable props on each map. Just to add some risk to gem hunting, you could add the possibility of a jump scare behind a prop instead of a gem that could disable the player for like 3-5 seconds.
Looking forward to future updates!