I played with another person for a decent amount of time to really see everything, here’s some thoughts.
gems → coins shouldn’t be a manual exchange by the player, it looks odd that a round can start, and someone already has the highest gem number since they didn’t exchange theirs. It should automatically award coins after a round since gems no longer serve a purpose but to be an intermediary currency.
The maps are quite small, six players at once might be cramped. I would lower the walking speed so that it doesn’t take only ~3 seconds to cross the map.
With how small the maps are, it would be nice to have walls the camera can pass through and see through semi-transparently, it’s quite a small box for the camera to be trapped in. Or force first-person only.
The audio could use some work, a single looping song isn’t as immersive as round-based music. A collectathon game like this is crying out for a satisfying sound whenever you click a gem, some sparkly effects as you collect it too.
The biggest flaw though… the gems are always in the same spots. It’s not much of a hunt, it’s a race to hit the same spots before someone else does. I’d imagine in a full load of players this would become unfair for a new player as a regular would have the collection process down.