• Librarians: for Enchanted books. It’s so much help in the beginning of the game. The best ones are Fortune (specifically to increase the amount of diamonds mined from 1 block), Efficiency, Mending, and Unbreaking. These will help you make the perfect pickaxe to mine mats. Silk Touch and Looting are great too. They sometimes trade library books, paper, and bookshelves which are nice too.

Everyone else has some unique trades that are nice too, but they are mainly around to trade for emeralds (to buy more enchantments)