yep, as a crafter you definitaly gotta learn to not keep everything you might need in the future.
only keep what's needed to skill-up, but don't forget to keep it to 1-2 different grind crafts at max.
especially when it comes down to grinding a craft job you gotta count in to have atleast 1000-2000 pieces of materials for each craft, for the next few levels.
i'm pretty good on inventory space on me and my 2 retainers.
1 retainer holds my crafting mats, one holds equip i don't currently use and items that i sell (fish/materials/etc), and on me i usually have the equip for my current class i play, and all craft tools/equipment.