Candy can be obtained in two ways. Completing a quest and searching for an item gives Candy. When an item is searched, the energy amount will vary per item. The amount of Candy will change too:

◾ 25 Energy - 25/6 Candies (Varies)
◾ 22 Energy - 5 Candies
◾ 20 Energy - 5 Candies
◾ 15 Energy - 4 Candies
◾ 10 Energy - 3 Candies
◾ 7, 5, and 3 Energy - 2 Candies

Make sure to spend as much Candy as possible. It can't be saved for the following quests.