Spreading Christmas cheer is the purpose of this game, and you do it using trinkets of your favorite characters from these shows, merging them to create more trinkets and unlock new characters. You will get the cheapest available trinket when you use the quick buy option, the one with number one on it.
You have to merge two trinkets with number one in order to make a number two, and then two with the number two to make the one with three on it, and so forth. Try to make these merges as much as possible to create new trinkets and this way gain stars in return. You also get stars by returning daily to playing this game and getting your daily rewards.