What are essential steps for starting a late thirties skincare routine?

[Avery_L]

I'm in my late thirties and after years of just using a basic cleanser and moisturizer, I'm finally seeing fine lines and dullness that make me want to establish a real skincare routine, but the sheer number of products and steps is completely overwhelming. I don't know where to start with serums, retinoids, or acids, and I'm worried about damaging my skin or wasting money on products that don't work together. For others who built an effective routine later in life, what are the essential, non-negotiable steps you wish you'd started with? How did you introduce active ingredients like vitamin C or retinol without causing irritation, and is it better to invest in a few high-quality products or try more affordable options first to see what your skin responds to?