Sunscreen is hands down the essential step in your routine. A lot of skincare can vary from person to person, but wearing SPF is the universal advice you'll get. It helps prevent wrinkles, fine lines, and signs of premature aging and, most importantly, protects against skin cancer.
We've said it before, and we'll repeat it: apply sunscreen every single day. UVA/UVB rays still pass through the clouds, and UVA rays can penetrate through the glass, so apply whether you're indoors or outdoors and whether it's cloudy or sunny.
Go for a sunscreen with at least SPF 30.