Ok so for enchanting items with elemental properties, obviously should require matching gems. Ruby adds fire, Sapphire adds ice, diamond adds lightning, emeralds could add physical damage ?
Make 'Enchant Gems' a Mundane high tier spell, a wizard casts it on a stack of gems, it costs 5-10 gems to create Enchant X gem. Crafter uses this as a compontent and can randomly get one of the three tiers depending on his skill.
Could have a Greater Enchant Gem spell, costing 5-10 of all gems to form a special gem for crafting, that has a chance to make the crafted item Engraved~Legendary, depending on merchants skill in his craft.
The SP and MP cost for these spells would be very high, as well as the stat requirement. Casting the spells could temporarily reduce the maximum Mp/Sp of the mage for a duration, so its not a spell to be casted lightly.
Could throw in a rare Reagent cost too.