In order to write an essay on any theme present in a novel, one must have evidence that points to the fact that the theme in question is really a theme. To do this, you need to gather support which justifies the theme of "the individual verses the society" from the text.
In the novel Bud, Not Buddy, the theme of the individual is found upon the first mentioning that Bud/Buddy is an orphan. This sets him up to be a person without a family, a name, or an identity. Therefore, he is an individual in search for who he is.
Outside of that, you would need to follow the things which happen to Bud/Buddy, and other characters, over the course of the novel which show an individual against the cooperative whole (or the community/society). For example, when a white family is offered food by the black community, the father of the family refuses. He states that they are white people and do not need handouts. This illustrates the idea of the individual (the white family) against the society (the black community).