So as the title says, once you finished downloading the patch, the servers come up, and you're back in the game what's the first thing you're going to do? Personally I plan on doing the main story quests first and seeing what's going on with all of that. Once I'm done with that I'm going to unlock the new 4m dungeons and give them an attempt or two before doing my expert roulette.

After that, I'll be queueing up for the 24m raid and later in the day I'll be seeing about my FC doing the airship exploration.