The green ball for the pets is hard to get filled back up. I don't think every animal should go off the same one they should each have their own. I also think you should make green balls to find which will faster reload.
That's simply not how Energy works, young Wizard. Your Wizard has a limited amount of Energy it can spend either on pets or gardening. Your Energy will regenerate over time or you can refill it immediately with the Energy Elixir. Remember if you remove a pet from the Shared Bank, your energy will be completely drained.
There are ways to get it filled up when you want it. 1. Leveling up ( you use up all of the energy then level up, giving you a fresh batch) 2. Energy Exlixir (yeah it's crowns ) 3. Waiting.... But yeah, everything goes off that one energy ball. Sorry. I suggest you just focus on one pet at a time.