If you need more Energy, here are some ways you can get some in the game without spending Gems:

* Daily Rewards

* Finish Quests

* Energy exchange machines using chocolate or fruit

* Create products in a Pot or Wind Juice Machine, etc.

* Dragon Pet Slots

You can keep earning more Energy beyond the maximum, but note that it won't recharge. It will only recharge when the Energy is below the maximum capacity.