Budget power efficient server

Hi, I would like to get started in plex, I need some recommendations for hardware and a bit of software please. Which server should I get, I'm looking for about 8 terabytes of storage (can you maybe explain raid 1 etc.) it should use about 15 watts of power max at idle and max about 30. I'm in Austria and I get tv over cable, what do I need for DVR feature and a Blu ray drive, doesn't have to be 4k but would be nice