This is what Gear Sets are for. You unlock Gear Sets when you unlock a new class. When you have put on the gear for that class, refer to the picture above and then click the +. When you want to switch to another Gear Set, just click on it and equip. You can drag Gear Sets onto your hotbar so that you can switch even faster.

The lodestone guide is at https://na.finalfantasyxiv.com/craft...thering_guide/