There are indeed a huge number of choices. It might help if you can give more information.
For example, what state are you in? Do you have some sense regarding what sort of major you might want for undergrad? Do you prefer large schools or small? What are your grades (unweighted GPA is better than weighted since the method of computing weighted GPA varies so much) and SAT or ACT scores?
If you live on-campus, then university will be a "totally new experience". Regardless of where you go there will be a great many new people who are NOT from your high school.
An increasing number of careers do require or at least benefit from grad school. As such, saving some of your college money for graduate school is generally a good plan.