To easily gain experience, once the Cave Of Ordeal has been opened, there are two stages that are "leveling stages" (Cave Of Ordeal 3 and Demonhall Mirror). Attacks that do a 3x3 moveable grid (3x3 specials that can be moved, such as Tera Star's square formation) or 3x3 attacks in front of the user (Winged Slayer, Astral Dance) should be learned. Make sure your ATK stat is high enough so you can defeat them in one hit, or have a high enough DEF stat so the enemy only does 0 to 10 DMG. Walk up to the enemies, align them with your 3x3 special, and execute it. Once you get to the point where they die in one hit, just repeat this over and over. For even more experience, pass the "Stronger Enemies" bill, but make sure they are not strong enough to kill you. Continue to do this to also gain a large amount of mana.