Applying for Classics at OxfordWatch
Honestly, I would just pick things that actually interest you. I was mainly interested in Greek literature, so I read quite a few plays by Aeschylus and Sophocles, and read through the Iliad and Odyssey. If you're more interested in history, philosophy or archaeology then that's absolutely fine - just read as much as you can and make sure to only mention things in your personal statement that you'd be happy to talk about!
You can try beginning to teach yourself either Latin or Greek if you don't know either of them already, but thats not a prerequisite - although it would be helpful as the course is very language heavy.
You could also go to museums or visit places of interest, but thats definitely not necessary as most people won't have access to these things.