I'm currently working through VCAA biology exams and averaging 60%. Marking slightly harshly but im worried. When should I see improvement and whats the best way to utilize these exams?
Don't worry, everyone starts off poorly at the start - making mistakes is a GOOD thing, because you want to be making them now so you don't make them on the real thing!
Never just work through one, mark it, and start straight on another one; keep a 'log book' of errors or something. So, if you make a mistake in the steps of transcription, write that down in your book, and that'll give you something specific to study. So next time, you won't do it again

You'll only make fewer errors when you start learning the information or skills you'd missed. Focus on fixing what's losing you the marks.
This is how I used them: Keep one (like the 2014 one) for a day or two before the exam, I think, but the rest I'd do earlier. Fill them out under timed conditions, then go through and mark them, writing in red pen every time VCAA puts the answer in a different/better way. I then kept them in a display folder as a question-answer booklet which was good to study off. You can do them again later, closer to the exam, if you want. Also, if there's a definition or good explanation in the VCAA answers, then STEAL IT and put it in your notes!