The Plex Pass unlocks hardware transcoding, which is a huge benefit alone. As others have said, it unlocks things like skip intro, credits detection, playing trailers before movies. It also unlocks the DVR feature, allowing you to attach an inexpensive antenna to your network and start recording over-the-air channels. It is very worth it.

The first thing you should do is get a dedicated server for your plex server software. I recommend the NVidia Shield Pro as your first Plex server host because it has excellent hardware transcoding capabilities. If you don’t want to buy the shield, you could get a larger server with a processor that has integrated graphics capabilities. Installing plex on that will actually give you a few more features and probably better transcoding capabilities, but it would be significantly more expensive.

After that, I’d get a Plex pass to unlock a lot of the good Plex features.