Set up a budget to compare the money you have vs. the money you plan to spend. Use a spreadsheet to organize your expenses vs. income. Break out your budget into categories such as:
meals or entertainment
splurges or big ticket items
Put aside a portion of your summer or school-year earnings for books in future semesters.
Consider ways to maximize summer earnings and investigate internship funding through Gettysburg's Center for Career Development. Think long- term: taking a lower (or even non-paying) internship may help you secure a more competitive job after Gettysburg.
If living in an apartment, have conversations before the semester begins about contributions to expenses. If living off-campus and paying various utilities or other bills, discuss and determine expectations for how and when roommates will share these additional costs.