Items make the world turn in FFXIV. You gather items to make items to make items, and sometimes use those items to make other items. You destroy items to make items. You battle enemies to make items. You trade tokens and seals to get items. You use items to get stronger, look better, and gain more riches
Most items are used by Disciples of the Hand. Even the ashes of a Bomb are used to make the strongest steel. The majority of items are collected by Disciples of War/Magic dispatching beasts across Eorzea, or they are harvested by Disciples of the Land.
Potions, Ethers, Antidotes...These are the staple of any Final Fantasy game. Alchemists will never run out of work, since adventurers never run out of wounds. In addition to helpful concoctions, there are also those that inflict enemies with Silence, Paralysis, and many other ailments.
Adventurers will always be hungry, thus Culinarians will have a lucrative career. These consumable meals provide amazing buffs.
Materia is used to strengthen equipment. Obtained by binding ones soul with a piece of equipment, then extracting it through destruction of the equipment, Materia is quite powerful.