the first thing was install FreeBSD. I have always been intrigued by it, a UNIX like OS that was by design meant to replace UNIX
FreeBSD descends from the Berkeley Software Distribution, a descendant of Bell Labs Unix. As it is very much a pedigreed Unix, you don't have to say "UNIX like". :)
Fun fact: The network sockets API that is (or was originally) used by every major OS for internet protocol support came from BSD.
Edit: You might enjoy these Unix family trees...
https://upload.wikimedia.org/wikipedia/commons/7/77/Unix_history-simple.svg
https://en.wikipedia.org/wiki/Satire