Still 2 retainers.
Just collect mats for lv51+ crafts, sell what you don't use or transer them to another character with the FC safe, and put the gears into the armory chest. And collecting glamour is optional and not releated to the amount of leveled jobs.
Also for glamour you don't use often, there is a cheap way.
Wait until 1-5 days are left for the sub, buy a retainer for just some cents (because of only 1-5 days), put the glamours into that retainer you don't need for the next month, but don't want to throw away, let the retainer sub run out and don't refresh it until you need the gear again.