You're getting a lot of shitty answers and downvotes, but you absolutely do not have to watch season 1 to jump into this right now

Adultery is kind of the point of this season, emphasized with those weird totems that were explained to us in EP 1. If that's not your cup of tea, I totally get it, depictions of cheating make me uncomfortable too, but the showrunners clearly have a vision of how they want these characters depicted. They're not glorifyin it though, I'm not sure that there's a single sympathetic character in the show, and that's the point they're trying to drive home. Think 'Its Always Sunny' but in a dramedy.