From an 4Gamer interview some time ago:

How many type of Gear Set are there to switch gear instantly?
Y: It’s actually quest based and at first you start with 1 and at timing where you learn the armory you get one more where you can use between two classes. Later by clearning quests the gear set will increase.

Is there a limit to amount of Gear Set?
Y: I believe it should match the amount of class/jobs being increased so currently we don’t have anything decided.

For those inside the Gear Set, will those be counted as items being carried?
Y: It won’t. So it won't show in the inventory .