This thread gives you an overview about the lvl 50 content and how the gear progression is: Click.
The first part is not really important you can skip to The Endgame Guide bit if you want. Also if you define 24-man dungeons as raid then there are none in the game at this point.(Crystal Tower comes with 2.1) The Binding Coil of Bahamut(8-man) is the current highest tier dungeon and very difficult so you can consider it as raid tier.