What are the best things I can do in my twenties to make sure my skin looks good in my forties (other than sunscreen!)

I'm 25 and only recently discovered this sub. It's fantastic! But all the info is a tad overwhelming! My skin is pretty good overall, occasional acne but nothing I'm too concerned about. But I'm starting to get worried about how my skin is going to age and want to know what is the best way to 'invest' in my skin now. I have read the FAQs but I find it difficult to tell the difference between anti-aging routines that treat current wrinkles and ones that will prevent (or slow) future ones. I'm notoriously lazy so I only want to bother with a routine that will pay off in the long run, I currently do very little to my skin, I never wear make-up so I even get lazy about washing it other than a rinse in the shower. I know I definitely need to invest in a good broad-spectrum sunscreen and apply every morning (and throughout the day as needed) but what else is worth doing? Vit C serums? Reitnoid creams? AHA exfoliation? Simple nightly cleansing and moisturising? Any advice would be greatly appreciated!