As somebody who hasn't done General 1/2, you are actually at a disadvantage as the key concepts in 3/4 are covered extensively in 1/2 as well. So from that perspective, your peers are ahead of you here. There is quite a bit of overlap such as the Core Module (e.g. Data - univariate/bivariate).
I would highly recommend making a start on the Data section, as this is one of the heaviest parts of Further (usually takes about a full term to complete). Assuming you're using Cambridge: these are Chapters 1 to 7 (just by reading how many chapters cover Stats, you can see why it's the heaviest). As it forms majority of the Core module, this is a compulsory requirement that you'll need to grasp to do well both in terms of SACs and both exams. The other bit of Core is Financial modelling & Recursion which covers Chapters 8 to 10.
In terms of modules, I would hold off on learning this at the moment. You may not even know what Modules your school has chosen yet. I am assuming your holiday homework covers the beginning of Data in prep for the first SAC when you return. Data/Stats in VCE often deals with heavy datasets which require analysis which is extremely time-consuming and tedious, this often stumps students as they may forget to include a data point by accident (as an example of how easy it is to make mistakes).
I also reiterate TheAspiringDoc's suggestion re: the CAS. It is literally going to be your saving grace when it comes to Further. You can do pretty much everything using it. You're allowed to use it during SACs, tests, exams etc. in addition to your bound reference in most cases. However in Further there is somewhat an emphasis on doing certain things by hand as well, so it's important to grasp both of these and not simply just rely on the CAS itself.
As you may know already, limiting mistakes is a core focus as a few mistakes can significantly impact your SS, particularly when dealing with exams. It really is important to know how to efficiently do things so you don't waste time unnecessarily. Further exams are quite short in duration and don't often allow you that much time to sit there and analyse every question in detail. Write your own bound reference, ensure you can quickly use the CAS (eg. either by using shortcuts or just having an understanding of how to do operations quickly) and limit mistakes.
I know "data" and "stats" sounds extremely simple but as a teacher of General, you would be surprised how many students struggle with these concepts. Don't underestimate Further. That's my advice, best of luck to you
