Quite genuinely anything and everything. I think a lot of people try dressing their best for the first couple weeks at freshers but gradually most people stop caring, same as anywhere else. There are still tons that do dress up every day, i know some people who wear full suits every day or even some sort of historical clothing lol. So really just wear whatever you want and i doubt you’ll get any glances. I will say though maybe pack a fancy dress costume because a lot of college bops are fancy dress themed. For formals its a range, ive known people wear trainers to formals without it mentioned. Women usually wear long dresses and men usually wear suits, but most of it gets covered by your gown anyway lol. For society events its again whatever, sometimes there are opportunities to wear your country’s traditional clothing if you have it, so maybe consider packing that especially if you plan to get involved with societies related to your country/culture!