>>96137219
Depends on what are they usually fighting, their combat doctrine and how common and powerful their magic is.
You don't want to have worse defenses than whoever you're fighting, particularly if you're an elf, who typically have low population and slow reproduction, so they should be even more averse to loses.
Going unarmored is fine in a duel, but agility doesn't help much in a mass battle or a siege. You won't have the space to dodge in a close formation, and if your formation is loose, you risk being overwhelmed by massed infantry or a cavalry charge. You'll want big shield to protect yourself from arrows or other projectiles, but that further limits your agility.
Mounted archers can get away with less or no armor if they can avoid melee, but they are still vulnerable to being shot back. Difficult terrain... mountains, jungles, deep woods... can be used for ambushes and limits the effectiveness of cavalry or large formations, so that may help.
Unless every elf soldier can use magic to match the protection of armored enemies, you'll want at least something, unless magic makes armor irrelevant. If you have enough mages serving as an artillery, massed formations and armor may not matter against volley of fireballs.
Layered or padded cloth or leather may be perfectly adequate protection for rank and file. Wood, bark, rattan, bone, maybe carapaces, shells and other parts of some fantasy monsters may also be used for armor. Stone is too heavy and fragile for armor, magic may change that. Ceramic tiles could be used as lighter alternative if you can make them durable enough. Magic to repel metal could be funny against non-elven opponents. Of course, if you're fighting other elves or someone with similar level of armor, it shouldn't matter.
