This is probably not relevant to you, but I think it's interesting nevertheless, so whatever. In Quest 64, your character's stats only improve when you perform an action that is tied to a corresponding stat. For instance, your physical attack damage would only increase when you use the staff to attack enemies. Likewise, your defense would only increase by taking damage. Your healing ability, which was tied to the water element, would only increase when you use it to heal yourself.
The agility stat is tied to the act of walking. Simply, the more you push forward on the analog stick, the more agility you accrue. The point is that you could go into a safe zone, like a town or something, then tape your analog stick at a 45 degree angle so that your character moves around in a circle, and leave the game on overnight in order to increase your agility. When you increase you agility, your character's movement space during combat increases, which allows the player to escape combat or get close enough to the enemy to use the melee attack, and you have a higher chance of avoiding incoming damage.