I study with no effort, and although that sounds stupid, I find it most effective.
Especially for science and math subjects, just by watching YouTube videos you effortlessly start to understand how everything works. Since you said you were an auditory learner, this will probably be your bread and butter.
For extremely syllabus based subjects such as business, memorize the syllabus inside and out (maybe more for year 12). I do this by creating acronyms. If you try and memorize the syllabus for around 10 minutes each day you'll see smashing results. (I can currently rewrite the business syllabus word for word lmao).