Algorithm uses 3 and 4 items (Reagents) for Tier 1. For Tier 2, it uses an additional 5th item. Tier 3 is not achievable from the current list of Reagents.
Armor: helmets, armors, gloves and boots
Necklace: all necklaces
Weapon: all weapons and shields
Click to select enchantment type.
You can unselect/select reagents by clicking each of them.