For me, BSD and Portage was my intro to "you're gonna need to learn how to compile stuff". But Gentoo Stage 1 was my real intro into how to bootstrap Linux. I had been using it for about 6 years at that point. (RedHat/Mandrake/TurboLinux/Caldera/Slackware/Debian-based stuff) Starting at nothing but a partitioned disk felt crazy. But I learned so much that not much in the Linux realm scares me these days. It made installing Arch back in 2011 a walk in the park.