While BESM is a classless system, there are certain common backgrounds or occupations availiable for characters who want to wander the world. Most people never leave the mir they are born in. Travel is dangerous and time consuming. Those who do wander The Unformed Lands were usually either born in a mage domain, expelled from their birth mir, or forced to survive a certain period of time in the Unformed Lands as part of becoming an adult member of their mir's society.
Characters who were born in a mage domain have a few advantages over the mir born. The major advantage is the ability to take more than two levels or skills in magic. They grew up in an area where magic works, and thus learned early on how to use magic. They will also likely have organizational ties or similar with groups that operate within The Unformed Lands.
Characters born in a mir, but expelled, will generally have few specific survival skills for the Unformed Lands. They will not know magic, but can have the ability. They may take only a single level of magical ability, and will be unskilled at it initially. Most people expelled from a mir were either socially unsuitable such as a non-conformist or criminal, or selected at random as a means of population control. As such, such characters will have been generally sold to slavers who sell them to various groups in The Unformed Lands. This is a good background for somebody who wants to play a changed humanoid since that is a common fate for outcasts. They will also normally have the disadvantage of marked until they decide to buy it off. They will also start off with no personal gear or items of power.
Characters from a mir that requires all young adults to survive in the Unformed Lands will have had non-magical training in survival skills and possibly magical training.