To get a very easy level up, go to the Scaraba Desert. Walk around until you see a little red bug which is the Criminal Catepillar. Try walking all the way to the bottom, straight back up, and looking to the right of the gate. It is very weak and will run from you so all you have to do is chase it around till you enter a fight. You will automatically win and you should receive around 28,000 exp. points! Keep finding and fighting him till you get to the level you want. If you get weak, go to the hotel and sleep to regain your health.