Newbie Guide:
Listen closely -- this is very important knowledge for a Dark Mystic like your self. Armor is divided into robes, light armor and heavy armor. Dark Mystics may wear armor any type, but different types of armor will affect your abilities differently.
When I refer to a set of armor, it means that the upper and lower body armor is of the same type. Robes provide little protection, but when worn by Dark Mystics they increase casting and movement speed, and even increase MP. With light or heavy armor, defense is increased, but casting speed, movement and MP are reduced compared to their level in robes.
These penalties apply only to upper and lower body armor -- helmets, gloves and other protective items do not cause penalties. With such items, feel free to use the strongest you can find.