Overall a very good clicker/idle game. Couple of thoughts:
1) The constant nature of gem drops and the linear nature of gold drops makes farming lower level creatures much more efficient and makes higher level creatures more of a pain than anything else.
2) The end-game is kind of disappointing, since the last creature just gets stronger and stronger until you can't kill it. I assume this is left here as a placeholder for expansion, but either way it's rather underwhelming.
Still a very well-planned and executed game. Kudos!