There are some skills that if you get good at them, they will make everything else easier and better. They are the sort of “foundational” skills for life, the ones that have the highest return on investment as their Nth order effects will be greatly distributive.
Here’s in my opinion a (almost) full list in a rough order of ROI:
Learning how to learn (including mastery and expertise)
Emotional intelligence + regulation
Experimentation and iteration
Health (sleep, exercise, diet)
Meditation (assuming this also helps with improving focus)
Building and breaking habits
Social skills + connection
Communication (writing + speaking)
Mental models
General financial stuff
The highest ROI skills seem to be ones that (1) compound over time, (2) apply across many domains, and (3) create multiplicative rather than additive benefits. For example learning how to learn 2-4x’s your rate of improvement in everything else.