So ...so much stuff

[Niqote]

-Don't craft at some point. Craft now. And use the leves to level (focus on the mats needed for them).
-Got materia? Thanks to the new system where we can unsocket the materia for 100% if they are grade IV and below, those (DoW) materia are now usually only worth thier NPC price. Dump them/send to alt
-Go through ALL your gear and turn in the things you don't absolutely need or love to the Grand company for seals. Spend those seals on ventures, exp tickets, leveling your squadron, whatever you need.
-Even if you LOVE a gear piece for glamour, go searching to see if there is a dyeable version of it, obtain that instead.
-Check the Calamity Salvager NPC and the one next to it, if they sell unique gear you obtained in quests, including event items. Throw them to the ground! You can buy them back for next to nothing gil. Event/Reward items that they dont sell must be put into the Armoire found in any Inn room or likely your FC house.

ANYTHING you have that you know you dont need but you simply want to keep just in case... Mail them to a friend, who in turn can mail them to your alt. Alternatively you can use a Free Company chest to transfer items between yourself and your Alts. Remember your alts have the extra retainers you pay for too.

If you want to go for Minecraft levels of organisation you could name your alts retainers easy names like 'Materia Potato' or 'Metal Roe-Bro'