What to wear in Dublin as a student?

Hey all, I’m incoming freshman from sunny California and I wanted to ask, what do you guys usually wear? Is it jeans and sneakers, or some other kind of pants and rain boot? what kind of rain jackets do y'all have, and do you have any brand recommendations? do y'all typically use umbrellas or no? Also, do people use backpacks or some other type of bag, and if you use a backpack how do you keep your stuff inside dry? Is it a waterproof backpack or something else? I haven't lived in a wet climate since I was 7, any and all information is helpful!!