read as many classics as possible. make sure you're staying on the subject which the question is expecting you to elaborate on, nothing else. no matter how well written your answer is, the examiner may only appoint 12/15 marks for both coherence and purpose if you stray off topic. this goes for every subject but thoroughly review your test results and work on whatever is lacking / causing you to lose marks. hope this helps a bit :)
i'd say start off with more accessible classics such as: picture of dorian gray by wilde, rebecca by du maurier etc. and work your way up from there, starting off with shakespeare would put just about anyone off reading. primarily tho, i kind of mentioned classics in assumption they were already somewhat of a reader. if anyone in want of advice is reading this, i couldn't stress it enough that ye don't jump straight into the deep end by reading classics if ye don't read regularly. there are amazing authors such as murakami and sally rooney whose works are simplistic but all around amazing and are great starting points. at the end of the day, reading absolutely anything, can boost your writing skills unimaginably. if anyone is in need of recommendations i'd be more than happy to help !