I am aware that many people know this. I posted it for those who do not know it. Do not rate it badly, please!
When you come to Endeva (a village almost at the very beginning of the game), then you need to buy a fairy from Rufus. What is your business. When you start, you can talk to the elf walking by the bridge. He has a point in the conversation: Train the fairy. After training, 9 experience and a few coins remain. When you come to Dunmore (the village in the swamps), then in one of the huts (Remember it!) There is a goblin that requires 60 coins for training. But he has a lot of experience: he has level 19 fairies. You can do this: earn 60 coins from the first (which is in Endeva), and then from the second (which is in the swamp) to train for the same 60 coins. Lots of experience for fairies absolutely free!