Also try to log out in a 'sanctuary' (that is, one of the three main cities, or a town or hamlet with an aetheryte) - each second you're in that area you will receive a 'rested exp bonus' that increases the amount of exp you gain in battle (when you have rested exp built up it will turn the xp bar from red to blue and gradually decrease as you use it up, but you can increase the length of the buff by staying in a sanctuary as much as possible (hence logging out in a sanctuary will eventually make the rested exp bonus add up).