a total must, but keep in mind that “waterproof breathable” is an oxymoron. You will be drenched in a downpour regardless, but a good jacket will keep you drier longer.
a total must
look for a sturdy sole. You don’t want flexible shoes as they will hurt your feet after hours of pedaling
a must. You will be thankful for having dry shoes and of course consequently dry feet. Tip: in a strong downpour, wear your rain pants with the shoe covers so that the water does not leak from the top of the covers.
Cycling pants, aka chamois
Will greatly extend the comfort of your buttocks on your saddle. Buttocks pain at the end of the day after 100+km of cycling is unfortunately unavoidable though.