Complex sentence: In the end, it is the jester who realizes that the princess thinks the moon is only as big as her thumbnail and made of gold, so he goes to the goldsmith, who makes a necklace with a gold sphere on it.
Split into simpler sentences: In the end, it is the jester who realizes that the princess thinks the moon is only as big as her thumbnail and it is made of gold. Then, he decides to go to the goldsmith, who makes a necklace with a gold sphere on it.