This varies. Usually the topics are very broad. Most students struggle with writing essays because of the grammar and sentence structure, in addition to trying to use complex words. Topics include: Holiday destinations, hobbies, interests, sports, tv shows, part-time jobs, celebrity etc.
In my opinion, prepare an essay for every possible question/topic, or at least a few bullet points on what you can possibly write. This will ensure you have encountered these main topics, which can be used to manipulate questions in the exam, and give you ideas on what to write.