Hi!
I recently graduated with a Politics & Sociology degree. I hadn't studied either of these subjects at A-Level when I started, so I had to do my own research on what was best to read before I began the course.
Firstly, I would recommend looking at a few of the key thinkers (Marx, Weber, Durkheim) and some contemporary thinkers (particularly C.Wright Mills) before you start. You do not have to be an expert in them by any means, but just having a basic understanding of them will help you a lot going into first year.
Secondly, a lot of the books by/about sociologists can be quite daunting, especially if you aren't familiar with the style of language used in sociology. Don't be discouraged by this. A lot of people who want to read Marx will try and read Capital straight away and wonder why they're struggling. I would recommend listening to podcasts, watching documentaries, and reading some smaller works/essays/journals to give you a basic understanding!
When it comes to essays, just make sure you engage with your tutor. It can be hard at first, but read every bit of feedback you receive, and if there is anything you are unsure of then feel free to ask them questions. I'm sure they will be happy to help.
Feel free to ask any questions, and good luck!
Michael