7-storage breakdown:
account1 main storage = everyday gear (for all 6 accounts), everyday consumables, everyday misc items (like gemstones, mora misc items, ammo), brew mats (account has dedicated brewer), some high-end sellables. (Storage is usually 580-600/600 - usually no more than 2 chars fully equipped at any given time - with hat collection spread over 2 carts on this account and 1 in account2)
account1 vip storage = place to dump stuff til I move it to the right accounts, job3 hats for this account (currently 21 on the account, dunno why super nubs and ninjas don't get job3 gears on job change...), costumes I don't use anymore, outdated "currency" items (like Sapha Certs), old non-transferable event items
account2 storage = spell scrolls, gems (e.g. Amethyst/Pearl/etc), color-themed non-dye items (don't ask), unused kafra shop items (mount leash boxes from Daily Quen)
account3 storage = unspecific misc item storage (including nearly 9200 Turtle Shells)
account4 storage = forge mats, upgrade mats, weapons to break via upgrading (account has dedicated forger/upgrader mastersmith), old forged items, dyes
account5 storage = sellables, spare armors, armor items not commonly used
account6 storage = cards! MVP/miniboss drops, consumables I don't use (including restoratives, buff items, GM scrolls, DBs, gift boxes, OPBs, OCAs, jewelry boxes, etc), jellopy and higher equivalents (including nearly 4800 cyfars), flower-related items (flower, illusion flower, witherless rose), non-color herb-related items (guillo ass poison herbs, ments, aloes, etc), old transferable event items
Keeping this organized keeps me busy, but I know where to find anything >.> Numbers usually run 300-500/600 items in each with highest variability in my dump storage.
I swear this is compulsive. Specifically demonstrated when I accidentally try to withdraw my whole pile of FWings which shoves them to the bottom of my consumables tab in storage and spend the next few grumpy minutes just reorganizing my storage to have items in the correct (non-alphabetized but highly specific) order.