Pick the protection plan first
The protection family is the first decision. Protection, Fire Protection, Blast Protection, and Projectile Protection conflict with each other on the same armor piece. General Protection is the common default because it helps against many damage types, but specialized sets can make sense for the Nether, creeper-heavy work, or projectile-heavy areas.
Do not mix protection books randomly just because they are available. Decide the role of each armor piece, then stage books for that role. If you want a specialized set, plan it as a set. If you want everyday armor, keep the choices simple and avoid turning every piece into a different experiment.
Handle boots as their own project
Boots are often the most complicated armor piece. Feather Falling is usually high value. Depth Strider and Frost Walker conflict, so choose water movement or ice walking before combining. Soul Speed adds another movement layer with its own use case. A perfect boot plan can become expensive quickly if every movement book is added late.
Stage the boots around the movement choice. If Depth Strider is the everyday choice, build around that and Feather Falling. If Frost Walker is for a special travel set, consider making separate boots. Separating roles can be cheaper and clearer than forcing one pair to solve every terrain problem.
Use Unbreaking and Mending carefully
Unbreaking and Mending are valuable on armor because the set absorbs constant wear. They are often worth including on each important piece. The cost problem comes from adding them after several other books have already touched the item. As with tools, support enchantments should be staged into the book tree instead of being treated as afterthoughts.
For each armor piece, test whether Mending pairs better with the protection book or with the slot-specific utility book. Helmets may have Respiration and Aqua Affinity. Boots may have Feather Falling and movement. Leggings may have Swift Sneak. Chestplates may be simpler. The best route changes by slot.
Plan slot-specific utility
Helmets can use Respiration and Aqua Affinity, which are useful for water work. Boots can use Feather Falling and movement enchantments. Leggings can use Swift Sneak. Thorns can fit on armor, but it increases durability pressure and is not always wanted. These choices should serve how you actually play, not just fill every possible slot.
When a slot has many desired enchantments, use the calculator before combining. A helmet with Protection, Respiration, Aqua Affinity, Unbreaking, Mending, and maybe Thorns has enough pieces that order matters. A simpler chestplate may be safe with fewer steps, but it still benefits from clean source books.
Build the set piece by piece
Do not try to plan the entire armor set as one mental operation. Choose the role of each piece, enter that piece into the calculator, and finish it with a safe route. Then move to the next piece. This prevents one complicated boot plan from confusing a straightforward chestplate plan.
Think about upgrade timing too. If a diamond armor piece will become netherite later, finish the enchantment plan while the item still has a clean history, then upgrade through the smithing table. If the armor has already been repaired several times, compare it with a fresh base before feeding it rare books.
Keep spare pieces simple. A backup helmet or travel boots can use fewer enchantments, which saves rare books and keeps the main set easier to maintain.
If resources are limited, finish the most important survival pieces first: boots with Feather Falling, the main protection pieces, and Mending or Unbreaking where durability matters most. A clean, finished partial set is better than four half-built pieces that all become expensive before they are usable.