Energy plays a key role as it fuels your actions on the island.

Over time, your energy naturally replenishes. However, if you're in need of a quick boost, head to the Booster menu: hit the plus button next to the energy indicator to grab an energy drink.  

Moreover, completing quests and fulfilling orders can earn you additional energy as a reward. Don't forget to explore chests during expeditions. Do you see some unusual objects on the island such as a sand castle or a pile of gears? Tap it and that will provide that extra energy kick!