i don’t want to spam the replies but i’ve lived in a cold and dark climate my whole life and had severely low vitamin D at one point because of where i lived, so if you want more suggestions than those i would def be happy to add on!!

seconding vitamin D. if sleep quality is a struggle at all, magnesium glycinate has been fantastic for me so far. i have also started planning winter-related hobbies, events and media i’m interested in ahead of time to give myself things to look forward to—lack of structure worsens SAD for me