As the posters before me have mentioned, I would suggest prioritising your tasks. So if you have your oral first, I suggest that you tackle that first. Now, when you read a text for the first time, you don't have to have a deep understanding immediately. The way I saw it was:
First reading - Getting an idea of characters and the general plot
Second reading- Understanding core themes, views, values and ideas
Third reading - Identifying embedded techniques within the text, as well as identifying the specific plot type and the analysis you will take on the text.
Obviously, you wouldn't expect to go into such detail with your Context texts, however that is just the way in which I tackle text response. I think after that writing notes from readings is important. Afterwards you can begin with some plans for particular prompts. At least in this way you can build much more confidence in your writing before getting into actual essays. Also, if you're stuck for ideas, read past exam papers and ask your teacher for some student essays.
One thing I can't stress enough - don't just do 'easy' prompts in year 12, well, the ones you find to be straight forward. Do the prompts you find really difficult, because at least now you can ponder about it with all the time in the world. Don't just think 'Oh this won't be on the exam', just do every single prompt you can get your hands on. Not only will this increase your confidence, but it will allow you to write fluent and detailed essays for anything that is thrown at you. I was one of two students in my 120 student cohort to write on 'Will you please be quiet, please?'. The other students in my cohort wrote about 'War Poems', and unfortunately had the experience of receiving two, very difficult, prompts. One of which I think was based on a poem that nobody studied, and the other containing a quote that no one knew of.
I am not trying to scare you here, just work hard and the marks shall prevail themselves!