YES

It depends on the rules the event has in place. Will you be allowed to resell later? Will you be allowed to make variations aside from what was in the machine? How popular is the event? Gacha works better with

some business models better than others.

the event is "I want to gacha", sponsored in full by : me!

in other words, no event, just actually found myself making something and coming up with a number of variation possibilities

MOAR PRETTY ROCKS PLS

I still love my heart geode. I'd play the hell out of a pretty rocks gacha

Dodecahedron terrarium but a number of rocks in it