Daily SPF application is the most evidence-supported cosmetic habit. It prevents sun damage, hyperpigmentation, and premature ageing more effectively than any serum or cream. Retinoids including over-the-counter retinol are the best-evidenced ingredient for increasing cell turnover and reducing the appearance of fine lines.
Consistent hydration and barrier support with ceramides and hyaluronic acid are foundational. The principle is to do fewer things consistently rather than many things irregularly.