Having more than 6-8 APs is overkill, unless you HS doesn’t have other challenging courses. In my kid’s HS, freshmen could not take APs, and Sophomore were discouraged from doing so. PE was require for 8 semesters, and so was lunch. So every day had, a maximum of 6 academic hours, and if any kid was looking at specialized advanced courses like Honors African American Literature, War and Literature, art courses, History of Hip Hop, Linear Algebra III, Investigative Research, etc, that limits the number of AP courses that a student could take. So, in some cases, focusing on AP courses at my kid’s HS can actually reduce the breadth and width of a kid’s education.
Your ECs should be a reflection of what you like doing. ECs do not have to be about whatever subject you want to major in, My Daughter will be majoring in Neuroscience,m and her main EC was dance, and her second one was the LGBTQ organization. Music is great, robotics is great, any sports is great, and it can be ultimate frisbee.
Most high schools will have a club day at the beginning of the year, and all the school organizations will have tables and try to convince you to join them. That is a great time to start exploring your interests and passions.
As for knowing what you want to do? My PhD adviser, one of the top mammal ecologists in the world, did his undergraduate in Psychology. Simon Levin, a great American ecologist and evolutionary biologist, did his PhD in mathematics. So, not knowing what you want to do in 8th grade is not something you need to worry about.
Choose courses based on what interests you. Math, biology, chemistry, history, literature, etc. Choose based on the level of the classes you took in middle school. You want to advance to the level above the classes you took this past year, if you were getting As and Bs,
Decide what you want to get out of high school and your decisions about your classes and activities should be based on that.
Don’t think “What should I do in order to get into the most prestigious college that will take me?” Think “how can I take advantage of the educational and extracurricular opportunities provided to me by my high school and by my community?”
You want to learn and to challenge yourself intellectually. You want to challenge yourself in other ways with your ECs. If you find that you can deal with the most challenging courses that your school has, while spending a lot of time pursuing your other interests and passions, without driving yourself to an emotional breakdown, then you should look for colleges which will continue to challenge you in the same manner. If you find that it is not easy for you to do all that, while maintaining your emotional health (at least so far as is possible for a teenager), a college which will demand that same level of academic rigor will not be a place in which you will be happy.
Taking the most difficult classes and crazy ECs in order to be accepted to a college with challenging academics is putting everything backwards. You try to be accepted to a college with challenging academics, because you were comfortable with taking very difficult classes while have a large number of ECs.
You should not set up your curriculum based on the college which you want to attend, you should decide your curriculum based on your strength and interests, and then choose your college list, based on what your transcript and profile is looking like during junior year.
Finally, @happymomof1 is right. It is never too soon for financial planning for college. College costs a lot, and it will just get more expensive.