Yeah, you definitely need to a strong foundation and be prepared to do a lot of work throughout the year. I'll tell you my experiences when I picked up 1/2 Methods in Year 10 (and then 3/4 Methods last year)
So at the start it was definitely a big jump from Year 10 Maths (which I moved out of at the start of the year) and I was struggling for the first few months. I remember being devastated by my 70 something percent for my first test and an 80 something percent for my second test, all because I ran out of time when the questions were quite doable. After having a pep talk with my mum, I decided to not only just do the homework questions, but to do a few questions more. Then I progressively started doing pretty much every single question in each exercise.
I actively sought advice from Methods 3/4 students and graduates who had done methods, as well as looked at advice articles in newspapers. I got a tutor as well, who provided me a copy of Maths Quest. So I ended up doing questions from both Cambridge and Maths Quest. The first few months of doing this much work was terrible, but I slowly adjusted and ended up getting a low 90s in one test and 100% in another test. Wherever I made mistakes, I would write a note to myself in red pen saying things like "Two decimal places not three!!" or 90% of the time "Silly mistake!!!".
Going into 3/4 Methods, I felt more prepared since I did the work in 1/2 and my brain was more adjusted to the greater amount of work that 3/4 would demand. While I didn't end up doing all the practice SACs my school gave me, I definitely built a strong foundation by doing almost all the questions in each chapter (especially chapter reviews, namely the extended response questions - since Methods can be pretty nasty in Exam 2). My teacher was also relatively good and she encouraged me to keep working at this standard.
Though in saying all this, I am quite guilty of procrastinating and getting behind a few times (and subsequently spending hours catching up). But I guess when it comes to VCE, that is almost unavoidable for everyone.
Also, in your case, since you're doing a language (which probably takes up as much time, if not more), it might seem a bit more difficult re: splitting study time and effort between them. Try talking with your Careers counsellor about this.
tl:dr, doing methods early is undoubtedly quite difficult (unless you're a natural at math, which I'm not lol) and it requires a lot of continuous hard work, but in the end when you get your study score, it would be all worth it!!
(P.S. I know I'm not qualified to give such advice for Spesh coz I haven't been putting as much effort into Spesh as I did with Methods last year, largely because I couldn't organise my time well aahhh ;-; *cries*)