up until season 5 episode 3 riverdale is practically a perfect show, certainly no episodes to skip. however, after season 5 episode 3, it may be for the best to skip all remaining episodes. the end of season 5 episode 3 isn't perfect, it clearly leads into the rest of season 5, teases you about what will happen in the next episode, but you will not find a better place to end the show after it. the rest of season 5 is still really fucking good, but it's not riverdale proper and the end of season 5 is an awful place to end the show, season 6 an even worse place to continue it. if, however, you want to watch riverdale up until the point it gets bad, regardless of ending, then by all means, finish season 5.
season 6 is really very aggravating, it is nothing like riverdale proper and if you care about the show you will find it deeply upsetting. the characters aren't ruined, many relationships are just as great to watch as in other seasons, but the rest of the riverdale universe is entirely ruined. i cannot, in good conscience, recommend anyone watches it. if 5 seasons isn't enough for you, just go straight to season 7. it does reference the happenings of season 6 at times, but the majority of it is an entirely new & separate storyline. it does not make up for any of season 6's mistakes, it is still in a ruined universe, but for most of it it's as if an alternate timeline riverdale. nowhere as good as riverdale proper, but it's fun.