Considering you're currently 2 years away from VCE 高考中文 make sure you know the vocab list back to front and know when a word means a certain thing or when it can't be used and etc. You want to use your brain power during SACs and exams to focus on what you're responding to, instead of trying to recall what a certain vocab means or how to write the character. Once you've learnt how to write a character and it's in your head, you can then learn the necessary grammatical conventions that character may require depending on the phrase or sentence and how to incorporate them
VCE Chinese SL Character List starting on page 14 of this pdf
Doesn't hurt to know the SLA vocab list too (when many are rote-learning the SL list in Year 11-12, you would have comfortably learnt it using spaced repetition (search up Anki and SuperMemo) in Year 9,10-11 so that you can learn the SLA list in Year 11-3/4 written exam and focus on your speaking skills (also developing your expression too, how would a native convey themselves, accentual subtleties (don't forget the tongue position/s too and you don't move your mouth/lips so much, the tongue does the hard work), intonation.
VCE Chinese SLA Character List starting on page 14 of this pdf
There's really no limit on the amount of words you know. Some may say you need to know 1000 words or 2000 words. But always be smart with the additions you make to your Chinese lexicon, make sure many of them can be used in a variety of situations or topics.
CCTV 中国中央电视台 is great for vocab exposure and to notice what vocab is most frequently used.
To score high in Chinese SL, personally I think it's not enough to just know the SL and SLA vocabulary lists. They are the most basic vocabulary that you're expected to know, but only knowing those words and nothing more won't get you very far. Apart from accurately answering the question, the only way to score high in the final exam (in the writing components) is to "wow" the examiner with accurate and sophisticated vocabulary, because everyone gets the same prompts, and your mark essentially depends on how well you have responded to the topic, not only content-wise but also in terms of language.
The best way to learn vocabulary is immerse yourself into the environment of the language - watch a lot of Chinese programs, although that would have been more beneficial if you did that while you were young, so your pronounciation is more native. Some good programs include 奇葩说 (第六季newest season), 脱口秀大会(第三季newest season) or 2019主持人大赛. Another good way of improving vocabulary is to watch 电视剧, from all different categories so you get exposure to different "types" of vocabulary.
古装 - 《庆余年》《琅琊榜》《楚乔传》《三生三世十里桃花》
现代 - 《我的前半生》《欢乐颂》
抗日/谍战 - 《伪装者》《剃刀边缘》《麻雀》《胭脂》
These are some of the dramas I've watched, all very good. Particularly the 古装 shows, they use a lot of fancy/formal/literary vocabularly.
Edit: Some shows aren't available on youtube (most are), but you can access them through 爱奇艺,乐视TV or some other platform.