Your undertone is either warm, cool, or neutral, and regardless of your hair color, it determines what colors look best on you (both in clothing and cosmetics).
Regardless of whether you like a full-coverage foundation or a light, tinted moisturizer with SPF, you should start with a clean, exfoliated, properly hydrated face.
Switching to safer skincare can seem daunting but start by switching the products that stay in contact with your skin the longest: serums, moisturizers, and sunscreens.