Hey there @lvjy!
Technically, you can self-study any AP class that you want. Common choices are history classes not offered by your school or science classes you may not have the time to take otherwise. You can find lots of resources online and the review books to help you study, and you may be able to meet with a teacher at your school to check your progress in your self-studies. Some of the APs that are typically regarded as being 'easier' include: AP Human Geography, AP Computer Science Principles, and AP Psychology.
Here is a link that has a guide for selecting which APs to take:
blog.collegevine.com/ap-classes-ranked-by-difficulty
I have taken 9 APs and it just depends on what your good at. If you like learning it and find it relatively easy try self studying it. Some classes of mine i have noticed are possible to self study are APUSH, AP euro, Ap comp sci A, AP world , AP Macro, AP psych and the Ap languages.
Hi! Have you considered APES?
To keep this community safe and supportive:
Yes, just be careful not to overwhelm yourself. Also, if you're planning to take the Psychology and Biology exams this year, it would probably behoove you to get started studying now. I would also definitely suggest taking Calculus BC in your senior year instead of doubling up during your junior year. The blessing of self-studying for these is that you can go at any pace you want, so you could also technically get a head start over the summer.