writing is hard due to time (the markers look for better vocab than how much you can write in 15min)
your story should be flowing and make sense but your plot does not have to be the best, as long as you put some big words in you should be fine
I don't think that's how you approach English. I tried doing that when I was in Year 8, ended up using words that were contextually innappropriate, had all these connotations which I didn't know of, and it just wasn't suitable for writing. Sorry to be harsh, but this is a very naive way about approaching writing.
Written responses are
not looking for how expansive your vocabulary is, if you eventually approach VCE English with that mindset you will be f*cked very severely.
Examiners are looking for
how well you communicate, how well you can support your argument, and how unique your ideas are. Vocabulary is merely something that embellishes your piece, but it's not the most important thing. If you write something that's logical, well thought out, and easy to follow, then you should expect high marks.
Here's some writing tips that actually help a lot:
Never use a metaphor, simile or other figure of speech which you are used to seeing in print.
Never use a long word where a short one will do.
If it is possible to cut a word out, always cut it out.
Never use the passive where you can use the active.
Never use a foreign phrase, a scientific word or a jargon word if you can think of an everyday English equivalent.
Break any of these rules sooner than say anything barbarous.