If you are not completely satisfied with the topics you are thinking about, which it sounds as though you aren't, you might want to research the era in which the book takes place, focusing on how the Civil War affected Southerners, socially and economically. The story's time and place are very much of the post-war era, and it might be interesting to learn more about that era. In fact, many issues that emerged after the Civil War continue to plague us to this day.
Certainly, for a research paper, you are expected to have sources beyond the story that is your focus. Otherwise, it would not be a research paper at all, but a literary analysis. I agree with the others who responded, that your professor should be providing you with clear guidelines and support as you write your first research paper. Some professors will, for example, state that you are expected to use some minimum number of outside sources for a paper. You should also have had some classroom time learning how to use MLA (used in most English courses) to provide documentation for your sources, which is a crucial part of every research paper.