What order do I play the games in?

Firstly, sorry for asking a dumb question but I've been trying to figure it out online, and I think I'm just confusing myself more and probably spoiling the games for myself.

So, I started playing rdr2 recently (I'm about 50% of the way through) and I know this probably isn't the ideal place to start so where do I go from here?

I was just gonna get the first redemption game to play after this, but I saw undead nightmare is included in that and the reviews seem cool for that but I'm guessing that's for after the main game? And where does revolver fit in, ik it's a separate universe but I would like to play them all - just wondering if there's a best order to go from here?