I'll be the lone wolf here and suggest you watch it all. Don't cherry pick episodes, at least not with this series, as others have said it's a highly serialized show and you will be lost.
For my money, the first half of season 3 where all the "heroes" are being rounded up was the best outside of season 1.
For my money, the first half of season 3 where all the "heroes" are being rounded up was the best outside of season 1.