This game could have been good, but is terrible because of things like the gates that needs a certain level. Its impossible to complete the game without using glitches to level up.
Instead of giving away free gems for skill reset, he could simply make skill reset be 10k gold OR 5 gems. That way he still doesn't lose gem sales, and people get happy.
This is indeed a great game. However, the fact remains that, if you released the full version for free on Kong, you would most likely earn the same, or most likely more than you are currently earning.