The player gains Experience Points (XP) throughout the game by winning fights. XP is used to level up and leveling up unlocks new equipment to buy and use. The amount of XP that can be won in fights ranges from only a couple XP to millions of XP.
The main sources of experience are tournament fights, challenge stages and storyline fights (boss battles and bodyguard fights). The other sources of experience are survival mode and duel modes, which provide barely any experience: it would take literally hundreds of thousands of games of survival or duel to level up in the later stages, since survival only ever provides a couple of experience points to a thousand - and when it provides thousands, millions would be required to level up.
After player reaches level 52 the maximum level, XP bar is replaced with the word "Max".
Here is a list of all the levels and the XP required to reach next levels: