Everything. MIT has open sourced their coursework so I took all of it. I studied, I worked my way through TAOCP, cracking the coding interview (less helpful honestly) and tons of leetcode, I spent 4 years doing this and interviewing to get an idea of the system architecture problems and see how I was progressing.

It worked, after 4 years of studying I landed a SF job and 6 months later I was at Apple, year after that I was at Netflix. You get out of this life what you put into it, and in software it’s all out there for you to get. You don’t need a degree, you don’t have to pass the bar or boards, you just need to prove yourself and be willing to hustle