I think I did a few of the older exams first to get a feel of the relative levels of difficulty and how the compared to VCAA ones. Then I kind of calculated how many exams I'd be realistically able to do and used that to determine which year to start at with my practice exams.
For example, if I had enough time for 20 exams and I had 5 exams for every year, then I'd start with the exams released 4 years ago. I figured this way I could get the more "relevant" exams done as well as allowing the first few practice exams to serve as a performance (eg. time management, accuracy, knowledge etc) indicator without feeling like I "wasted" the "better" exams.
After that, you should have a pretty good idea of which trial papers are not worth doing and which ones are "better". Alternatively, you can search atarnotes forums and see which companies' exams people are recommending xD. If you still have time left you can just pick out the better exams and attempt them.
To be honest by this stage of the year I think I had done most of the VCAA papers indirectly via checkpoints (used for SAC preparation).