[Viliam1234]

It is tempting to say "everything", but acquiring knowledge takes time, so you need to prioritize. I would recommend the following areas: (note: the order does not imply priority; I would rather recommend to do this in parallel, like get the most useful 20% of everything first and then go deeper)

* Keeping your body alive and healthy: what to eat, how to exercise properly, how to avoid diseases, how to avoid crime.

* Keeping your mind sane: how to think rationally, how to avoid mental traps (cults, scams, political mindkilling, superstition... i.e. various forms of manipulation and self-manipulation), what makes you happy and productive, how conditioning works.

* Gathering power: social skills, financial skills.

* Meta skills: how to acquire skills faster, prioritizing and managing your time...

And perhaps computer programming as a starting skill -- something that will nicely pay your bills until you become sufficiently great at the remaining skills.