You also need to do well in your A levels but that's already standard. The main problems you want to tackled for Oxford is the interview and LNAT. I suggest practicing for it because it's a heavy weighting in their decision making but you dont need to do this until the summer. The second is getting stuff for your personal statement and interview, which is easy to do. You can do a lot of things like reading cases, legislation, judgements, books, articles, news, academic reports, doing essay comps, your own research project, EPQ, watching documentaries, listening to podcasts, lectures, TED talks, doing online courses, summer schools, taster days, work experience - honestly there's so much you can do. Dont think about what you need to do to stand out but finding things that could fuel your interest in law because in my opinion, a genuine interest in law, especially in specific areas they are interested in, would make you stand out from those who havent researched about it, done generic stuff or wants to be a lawyer. The Law enrichment course wouldnt put you at a disadvantage at all tbh.