Minecraft wiki entry for Things_not_to_do, associated text: Diamond is the best candidate for enchantment in most circumstances, so if the player has enough diamonds, it is always good to enchant diamond armor and tools first. Level 30 enchantments are usually the best since they usually output the highest levels of enchantments. Enchanting pickaxes early on can greatly help the player, as they could get the Fortune enchantment on their pickaxe which would increase their diamond output when they mine. If the player has run out of diamonds to make into gear and enchant and they do not want to waste their experience, a good candidate is a bow or a fishing rod. Since these items do not have tiers, the player is still making sure that they make the most out of their experience points. And then when they do get enough diamonds, they can use those. Netherite and gold-tier items, and iron tools, have a higher enchantability than diamond, though.