Best enchants to aim for on armour and tools in Minecraft?

anvil order matters more than people think. every time an item goes through an anvil it gets more expensive to work on, so combine books together first and then put the finished book on the item, instead of adding one book at a time. that's how you avoid the Too Expensive message on a fully kitted pick.

Mending and Unbreaking III on literally everything, those first. Armour: Protection IV on every piece, Feather Falling IV on boots, Respiration and Aqua Affinity on the helmet, Depth Strider on boots if you're near water a lot. Tools: Efficiency V, then Fortune III or Silk Touch. Sharpness V and Looting III on the sword. Conflicts to watch: only one protection type per piece (Protection, Fire, Blast and Projectile Protection rule each other out), Fortune vs Silk Touch, Sharpness vs Smite vs Bane of Arthropods, Depth Strider vs Frost Walker, Mending vs Infinity on a bow. Most people keep a second pickaxe for silk touch. Swift Sneak and Soul Speed don't come from librarians, you get those from chest loot, so don't hold the trading hall waiting for them.