I feel I should make things clear before everything starts to get complicated.
These are the differences between the classes. in order to graduate to the next class, you must accomplish the objective stated next to them.
Moreover, each class had ten levels. Each level is 3 times more powerful than the previous level, and therefore 3 times more difficult to complete.
I will not mention what happens when one is both a Black Class, and a Magi class, because that would be spoiling later chapters.
...sorry, I can't seem to get rid of this blank space. Darn my level one White class programming skills!