This is what I send people when they tell me they haven't read Slate Star Codex and don't know where to start.
Here are a bunch of lists of top ssc posts:
These lists are vaguely ranked in the order of how confident I am that they are good
https://www.slatestarcodexabridged.com/ (if interested in psychology almost all the stuff here is good https://www.slatestarcodexabridged.com/Psychiatry-Psychology-And-Neurology)
I think that there are probably podcast episodes of all of these posts listed below. The headings are not ranked by which heading I think is important, but within each heading they are roughly ranked. These are missing any new great ACX posts. I have also left off all posts about drugs, but these are also extremely interesting if you like just reading about drugs, and were what I first read of SSC.
If you are struggling to pick where to start I recommend either Epistemic Learned Helplessness or Nobody is Perfect, Everything is Commensurable.
The ‘Thinking good’ posts I think have definitely improved how I reason, form beliefs, and think about things in general. The ‘World is broke’ posts have had a large effect on how I see the world working, and what worlds we should be aiming for. The ‘Fiction’ posts are just really really good fiction short stories. The ‘Feeling ok about yourself’ have been extremely helpful for developing some self-compassion, and also for being compassionate and non-judgemental about others; I think these posts specifically have made me a better person.
Posts I love:
World is broke and how to deal with it
https://slatestarcodex.com/2015/08/17/the-goddess-of-everything-else-2/ (read after moloch stuff I think)
Feeling ok about yourself
https://slatestarcodex.com/2018/04/01/the-hour-i-first-believed/ (this is actual crazy, read last)