I would try to pick between the change and splitter. They both serve the same purpose (change of speeds with fastball action). Hitters will sometimes pick up the splitter earlier, so if the change is good, work on that and make it even better.
Don't hesitate to contact schools as well that you might be interested in. Remember, there is a whole country of schools out there. Take into consideration all aspects of college life. Location, weather, student life, academic programs, and baseball program. When it comes to baseball, make sure you go to a school that you will get better at and will make sure you stay on track in the classroom.
College camps are a great idea as well as showcases. It's kind of late in the game being a senior, schools have got most of their scholarship money gone by now for incoming freshmen. Keep an open mind when talking to coaches and use your grades act/sat scores to your advantage. Walking on is always an option as well, but you have to be enrolled at the school before you try out for the team.
Good luck this season!