I have no idea. The basic Four Job Fiesta run has you go to the Wind Crystal, tweet to Gilgabot #Wind and get a Wind job, then #Water for water and so on and so forth. There are various other types of runs (Natural which means Bartz keeps the Wind job because he has the Wind crystal's essence, and so on for the other three, Upgrade which means you get your Wind job then when you tweet Gilgabot #Water you can no longer use the Wind job, or Classic which means you only get the FF1 jobs, etc.)
But Chaos? Yeah the only person who knows how Chaos works is the guy running the Fiesta and he ain't telling. People were saying how it worked last year, but the guy running it straight up said "The thing about Chaos is that it doesn't have the stay the same mechanically from year to year" or something like that. So I have no idea what to expect. The official site literally only describes it as "The player will be assigned jobs."
Outside of that? IT IS A MYSTERY