Don't study the holidays before your first ever semester at uni. You've just finished VCE, a culmination of probably 2 years of hard work and stress, so its time for you to just chill.
First semester of uni for first year is more or less like a test run, where you get to know what is required of you in semesters to come. For first year first semester biomed UoM, there isn't much you can prepare for, since the biology core is run from the ground up (this is to accommodate non-bio background students) and chemistry is a different story to VCE chem. For your maths elective (depending on your pathway), there isn't much methods/specialist and even so its not worth worrying about since you will be confused on how to learn material in a way that complements the course.
One thing to prepare for is to plan your timetable and to get up early on day of class registration for next year. The following website:
https://sws.unimelb.edu.au/2016/ gives you the classes which will be available for your subjects, thus you can sort of plan ahead and you will be able to select the classes you want on registration day, but they can change without notice. For biomed especially, where you get around ~20 contact hours a week, you'd ideally want a good timetable with a legit day off or so. Otherwise you'd be hitting the chem labs at 6:30pm at night and have really f'ed up clashes and ridiculously long breaks.
Uni jaffy life has more freedom compared to school life, which is rigid. You can bail/wag lectures, leave stuff to the last minute, and leave legit studying for exams until swotvac (for jaffy year/first semester). Of course, this is if you really wanted to; it's definitely not a recipe for HDs. One thing though, you should definitely make an effort to rock up to your practicals, which marks attendance and are hurdles, and also to your tutorials (15-25 students; classroom setting), where you probably learn more stuff than in lectures themselves. Check the unimelb handbook to identify which things are hurdles or not since they are different across subjects.
As for competition, thus far, it hasn't been as intense as VCE. University is more about yourself and not your peers. You have to make an effort to understand things yourself and not rest upon on how well/bad information is taught. You can have bad lecturers who explain convolutely, and yet you'd be expected to know material that they have mentioned. As for exams, some lecturers say that anything they say is examinable, and this is not just the lecture slides. You have both in semester assessment which accounts for a certain percentage of grades, and then you have the exam, which totals to 100%. The thing is though, not all assessment/exams are scaled. Also, nobody cares if you don't know jack, its just makes attending lectures useless since you are too behind to follow.
TL:DR - take it easy, you've just finished VCE, plus there's not much you can study anyway. Make the most out of first sem to get a real taste of uni life.