"I've never seen this show before and now I'm starting with episode 246?" Been there. Everyone's saying how great "Supernatural" was (around season 10) so I download season 1, then 2 and ask "When does it 'get good'?" The answer seemed to be "season 7". Watching more than 100 episodes ready for it to get good didn't appeal.
I started Supernatural with season 4 and then went back to seasons 1-3 and didn't really think it was that good, funny enough for me Supernatural started to go downhill with season 6