piracy starter kit - old head getting back into it

I have a bunch of old bare hard drives with tons of content sitting on them, and I was thinking about setting up a new NAS / piracy Linux box, as a backend for Plex or similar.

I want to be able to index my old content and automatically grab new episodes of TV shows and popular movies, with minimal fussing around after initial setup. I am capable with technology, so happy to spend time getting it set up in the first place.

Where should I start?