Pick Your best skill on each event prior to the competition and make it your focus. Put yourself through each routine as Aussie_coach suggests, and while imaging, consider the skills before and after your "Marquee" skill as the introduction and curtain call for that "one" skill you do best. It really doesn't matter if it's a forward roll or a full twisting from lay out, just do that one skill better than anybody else, make that you entire focus. At that point your nerves are channeled into a positive purpose, because this is your opportunity to show how your best skill should be done, and the rest of the routine is there to make that presentation a success.
I know it's just your first competition, but you are going either because you deserve it, or your coach is an idiot. So unless you think your coach is...............
Go have fun, and be proud of what you can do!