Welcome back Zhanatos. You missed quite a bit, so you'd obviously first want to review the patch notes.

The biggest changes are the phasing out of Tomes of Philosophy, and the addition of tomes of soldiery. A lot of the raids like Crystal Tower and Coil are no longer on a weekly timer so you can grind those to optimize your equipment. T5 is still a difficult chokepoint for players to pass through, but there's a 20% crystal buff for it now. At i90, you are capable of running all of the content except for the second coil of bahamut, t6-t9 (although i91 is debatable for t6 depending on how geared your party is). There's also a lot of EX primals and you don't need to finish Titan EX to continue tothe next arc: Moogle, Leviathan, and Ramuh EX.

As for gearing, it's easiest to grind Soldiery and Syrcus Tower every week for i100 gear. At the same time, try to do the weekly hunts too. You will be able to buy 'Sands of Time' to upgrade your soldiery i100 to i110 using Allied seals.