Each time you level up, 100 experience points are needed. This is helpful because if you are very weak (at a low level) you will earn a lot more experience points. Note - Try training somewhere you think is best for your level. If your level is high, try Capsicum Caverns on Razen, the fire planet. If you are at a low level try the woods on Gren, the wood planet. Keep in mind that the maximum level is 99.