Fire: Equip the character's weapon with an Elemental-Ice combination and have a Fire Ring or Fire Armlet equipped. Basically, attack with Ice, absorb the Fire attacks for HP points.
Lightning : Mechanical enemies are very prone to lightning attacks. Usually the fighting with just Lightning spells against mechanical creatures are enough to bring down the enemy is just a few turns. Equip the player's weapon with Elemental-Lighning combination, and either a Bolt Ring accessory or Elemental-Lightning in their armor. This should adequately protect you from their lightning attacks.
Ice:When in the Gaea Cliffs and the Great Glacier, having this setup is effective. Equip all your characters with the Elemental-Fire combination in their weapons, and either Elemental-Ice in their armor, or an Aurora Armlet. Also, the accessory Ice Ring is effective here for healing purposes.
Dark: There is a few enemies that are dark based, including Demon's Gate and Gi Nattak. There is little that you can do early in the game to effectively attack dark enemies, so outfit yourselves with your strongest armor. Later on in the game, when you fight against Dark Dragons, equip Elemental-Alexander in your weapon. While attacking these dark enemies, your attacks should be double or more in intensity.
Poison: Poison attacks are damaging because they ebb away at your HP. Healing the negative status of Poison by using Poisana or an Antidote may work, but chances are the enemy will poison you again after a few more attacks. Protect yourself against poison by either equipping a Star Pendant or a Poison Ring accessory. Having Elemental-Poison in a character's armor will help reduce or absorb the damaging effects. Also, remember that a Poison attack against a poisonous enemy will do nothing to harm it.
Physical: Some attackers use only physical attacks. The best way to protect yourself from these attackers are to use your very best armor with the highest amount of evasion (defense percentage). Place a Long-Range Materia in a single slot if you have any, and place your characters in the back ranks. The strongest physical attackers in the game are the Iron Men in the Crater.
Good luck using your armor and weapons to their maximum potential. Also, the two most strongest defensive armor pieces are the Mystile and the Imperial Guard. Make sure you look out for them!
Armor That Can Be Bought:
