2 of the same level item and an enchant stone. Spirit Armor + Spirit Armor + Armor Enchant Stone = Spirit Armor +1 (or +2/+3 in very rare instances)
The amount of stones required goes up with each level of equipment, though. Combining +1's requires 2 stones, combining +2's requires 3 stones, etc.
The amount of stones required goes up with each level of equipment, though. Combining +1's requires 2 stones, combining +2's requires 3 stones, etc.