Archer -
Classification: Light armour
-Hide (Very Basic: rags, shoes, etc.)
-Fur (Basic: armour, boots, helmet, etc.)
-Leather (Normal: armour, boots, helmet, etc.)
-Rangers (Advanced: armour, boots, helmet, etc.)
Mage-
Classification: Robes
Should be different types of robes, each which gives different benefits while offering limited protection. E.g extra MP regeneration. Hoods should also take the place of helmets, and they can also sometimes wear capes An example of a name is perhaps 'robe of the magi'.
Warrior-
Classification: Heavy Armour.
The basic set is usually helmet, body armour, boots, gauntlets, which in order of protection is usually Bronze, Iron, Steel. Depending on what creatures are in your map, you should also add armour specific to the creature e.g Elven armour.
The thief is similar to the mage, with cloaks instead of robes, which give benefits specific to the class.