How can I improve my senior year and get accepted at USC?

Next year i'm going to be a Senior, and I'm wanting to attend the University of South Carolina. So far my overall GPA is around a 2.8, I want at least a 3.2 my senior year; so that my overall will become a 3.0. I haven't took the SAT or ACT yet but I will in the fall. I'm a little scared about taking Algebra 3 next year, because I struggled in Algebra 2 and passed with a D, lastly what are some good extracurricular activities that will look good on my transcript? All that i really done in high school is play rugby, and some jv football.