I was making a similar amount of mistakes leading up to the exam and ended up getting a 50, so here's what I did:
Every time I made a mistake I would write it in the first page of my summary book in words and/or with diagrams or what ever I need, saying what type of question it was, what I did wrong and what I should do whenever I see a similar question. Because both the exams used a summary book, I would also have my summary book with me whenever I did a practice exam. The 'mistakes' section was split into the different topics, so every time I would, for example, start the graphs & relation section of a practice exam, I would read through that mistakes section before trying to answer that section, so I hopefully won't make the same mistake again. I even did this in the exam, since if you're quite strong at maths you shouldn't be pushed for time, so it is definitely worth it. After doing most of the available VCAA exams plus a few others, you'll have a pretty good log of all the different mistakes you can make and hopefully it'll help with avoiding them.
