Dixon textbook should be just fine. Tim Riley will also be good in conjunction since both books often cover certain aspects of topics in more detail than another. The questions there should be fine but I didn't really do them, getting prelim past papers will suffice and be more effectively for exam technique rather than the textbooks.
As @ExtremelyBoredUser has said, both Dixon and Riley are fine. However, I'd skimp out on buying the updated prelim textbooks. The main carryover from prelim to HSC are just a few core concepts and not so much the statistics. Searching for internal assessments on thsc will also suffice for practice.
Honestly all the textbooks are kinda shit, you could prolly pirate the Dixon textbook and use that to build a rough foundation, but to gain a solid understanding I would point you to youtube channels like MR University that explain economics really well (they often cover stuff outside syllabus but honestly it really does help in terms of understanding economics generally). Exam style questions, for prelim you only really have past papers to go off, I highly rate Fort St, Sydney Boys, Baulko and Grammar papers as they mimic the HSC the best
Are there any places where you can freely access said Fort St, Sydney Boys and other eco past papers?
thsc