Hey there,
I would start off with holiday homework first, and then potentially get a head start on the first area of studies for each of your subjects.
ATAR Notes are currently offering revision lectures in mid-January which are a helpful resource to start the studying! [https://atarnotes.com/lectures](see here for more info 🙂)
Otherwise, take it easy and enjoy your break so you can come back to school refreshed and ready to get into some studying.