It ain't really a cheat it's more a training hint:

If you finished the quest of the king of Ascantha (make him happier) go back to the mountain where you neede to enter the moon realm.Don't go to the top but just below the top and let Yangus whistle. Several monster (minimum 3) shall come attack you, defeat them and you shall receive atleast 30 gold and 100 experience after the battle.This is much at that time for most of the players.Do this as much as needed.This will to be useful on you're quest later you'll defeat enemies much easier.

Do the same thing at the swordsman labyrint where it's 100 gold and 200 experience.

For the pro's (lvl. 30+) they can go to Savella Cathedral and do the same thing.Morrie's place has the same effect.

At all of this locations there are to Metal slimes so try this it really works.