To my younger self: you'll converge on these upstream skills later. You have a limited amount of focus and these synergize well. To whatever extent your special interests are aimable, these are good targets.

Econ - you basically already know this is important. Micro, history, behavioral, finance, and running a small business.

Relational - this one you definitely don't know is important. Read a couple books on communication patterns and attachment styles. Find a context to do peer therapy and learn about how others affect you and vice versa. Many invisible gotchas.

Contemplative - investigating your own mind. You're right to be skeptical of a lot of the material out there, nonetheless there is some good in it. Find the people trying to be careful.

Pedagogical - how you learn everything else here and how you teach others anything. Honorable mention subskill of business writing, principles of succinct communication of complex topics.

Creativity - becoming more generative and the very important skill of ambiguity tolerance. This also helps everywhere. At the technical end it also relates to managing ambiguity, think How to Measure Anything

Expert Judgement - who should you listen to? Which sources do you actually want to marinate your brain in? The autobiographies of interesting thinkers are a good start, keep going.