Nothing too exciting. Perhaps counter-intuitively, tech giants are the most straightforward to get into because their interview focuses so much on whiteboarding ability. I personally know people who have gotten into Google/Amazon/Facebook straight out of bootcamp because they had great ability to solve these sorts of problems.

My personal journey took ~2.5 years. I didn't think it was possible to get into a tech giant out of bootcamp so I never tried. Worked two different jobs for a year each, figured I'd give the interviews my best shot, and got accepted.

For background knowledge, I used Algorithms 4th ed. as my textbook. My source of practice problems was LeetCode - did a few/day over the course of around 6 months leading up to the interview.