For me, besides creatine which has been genuinely transformative at age 50, I've gained a lot more from the stuff I've dropped (dairy milk, ~2/3 of my caffeine (mostly by drinking reduced-caff coffee or tea and eliminating soda), sweets of course) than stuff I've added. But of the latter, I'd say fiber and fruits have been the biggest additions, partly in themselves and partly that they make it easier to avoid the bad stuff. I tried experimenting with a few other supplements, but most of them were meh at best.

So, "take things to the next level" with some pears and oatmeal and chia seeds! Now I just need a sponsor.