Rewards from leveled up is almost useless especially when you already on high level. You'll need more than 1 reward to upgrade 1 item. When you can't even get more *3, then you'll find the game slowly become so boring because it feels repetitive, when you've familiar with the pattern, it's not even challenging anymore, and you stuck there because you don't have enough crystals to upgrade/progress. You have to wait for level up rewards, doing achievements, etc. just to get crystals. *Casino sucks