I don’t think any of us here can guarantee you admission to the UK university of your choice. Applying to universities is certainly an inherently stressful and uncertain process.
Just do the best you can to get a solid HS education, and take the AP courses available to you that you are genuinely interested in and think you can do well in. Take the SAT IIs in areas you think you can do well in.
Look at the webpages for universities you like, and look up the courses and related courses and see what you would like to apply for. Throw your hat in the ring. That’s all you can do.