Instead of spending millions of gils in getting the materia, you can spiritbond gears and get materia yourself.
lvl 45+ gears will have a chance to give tier 4 materia, and it's 10 times faster than spiritbonding i55 AF gears.
Also it's way faster to SB your gears when it's in HQ and if you meld them with junk tier 1 materia (30% faster)
You can basically SB a full set in 1 hour of farming.
Crafting Gears:
Head: Patrician's Wedge Cap (weaver)
Body: Patrician's Coatee (weaver)
Hand: Patrician's Glove (weaver)
Legs: Patrician's Bottoms (weaver)
Feet: Patricians' Gaiters (weaver)
Belt: Raptorskin Merchant's Purse (LTW)
Subject: Spiritbonding Gears for Crafting Materia