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.
Gears for Gathering:
Head: Cobalt Mesail (ARM)
Body: Raptorskin Jerkin (LTW)
Hand: Fingerless Raptorskin Gloves of Gathering (LTW)
Belt: Raptorskin Survival Bel (LTW)
Legs: Raptorskin Culottes (LTW)
Feet: Raptorskin WOrkboot (LTW)