This might be late, but I have experience with the subject (self-studied my freshman year, got a 4). I found both CrashCourse (https://www.youtube.com/playlist?list=PLBDA2E52FB1EF80C9) and GetAFive (https://www.getafive.com/ap-tests/world-history) to be very helpful. I also used the Barron’s book and TeacherOz’s cram packets (http://www.teacheroz.com/apexamreview.html) at the bottom of the page. Hope this helps!