In Red Dead Redemption for PS3 and Xbox 360, there are some high stakes games in Blackwater that can’t just be joined by anyone. You’ll need “proper’ attire to join, specifically the Gentleman’s Attire.
To get the Gentleman’s Attire, you just need to sign up for the Rockstar Social Club online community. Yes, that means you’ll need to be able to get online with either Xbox Live or Playstation Home.