I suggest you leave prelim to the big holidays since you would of just finished year 11 now. Take a break from it for now so that way you come back to it nice and fresh. Sometimes if you focus on something too much your brain kinda shuts off. Besides, most past papers I've seen barely ask for year 11 content (about 5 marks, usually MC) , so don't stress too much.
But starting the first topic for year 12 is great! Focus on that for now, and if you can try to finish it before year 12 starts. It'll be a great boost!
Also, don't overload yourself otherwise you'll burn out quick. My biggest advice and I know this from myself, if you need a break, TAKE IT! These are the holidays, so enjoy them. Balance is key! Even during school, if you need one day to kick back, Do it!
Also, go to past hsc papers and collect questions for topic one and try to solve them. If you're ever stuck understanding a concept and can't access a teacher, youtube is your best friend. Also, to do well in maths you must practice solving questions. By comparing your solutions to the answers, you become more aware of how to tackle questions. There will be times where you are totally off, and that may make you feel demotivated, but that's okay! Don't let that affect you. Remember, you'd rather stuff up now and learn from your mistakes rather than stuffing up in the exam. Just by putting in that effort you are progressing without realising.
Another valuable resource which I highly recommend is ACEHSC, here:
Not only can you access past papers for maths, but trials (usually harder than HSC, so better to practice) and even assignments and notes. This applies to most other subjects too, such as chemistry.
Best of luck in your studies!