Yeah, PomPom has the right of it. If you arent sitting on a stockpile of Poetics from before you left then you can grind some out fairly quickly. The roulettes for Leveling, 50/60, Trials, Alliance, and (god forbid) Main Scenario all pay poetics at your level. A couple days of running as many of them as you can would put you in good shape. You can also get them from A and S rank hunts if you can get into a hunt train. Alternatively, you could spam a couple of the dungeons that youre comfortable with that have good poetic payouts(something like ARF). And the new player bonus is paid in poetics too(for cap activities), so if you never ran the coil/alex cycle and dont mind doing them unsynced a good PF group could get you a couple thousand in the space of an hour or two. So gearing up really shouldnt be too hard.
As for picking the class back up, a couple big changes happened to BLM while you were gone. Cross class skills were replaced with Role Skills, so youll want to take any removed skills off your hot bars and slot in 5 role skills that fit you. The biggest change was to Enochian. Eno is no longer refreshed by casting B4, now its a buff that once activated stays on you as long as you carry either your astral fire or umbral ice stance. Any level of umbral/astral is fine to keep Eno, and switching between them is also fine - you only drop Eno if you no longer have either stance active. AF/UI were also extended to now last 13 seconds, and the recast on Transpose was dropped to 10 seconds(can be used to save Eno in an emergency, or to carry it between monster packs). We also got a change to our DoTs. Thunder 3 now automatically replaces thunder 1 if youre high enough level to use the higher one, and thunder 2 is now an aoe(it procs thundercloud at a lower rate, and you can use a thundercloud proc on it). And finally, B4 got a new mechanic added to it(since it lost refreshing Eno) called Umbral Hearts. At your level, they reduce the cost of fire spells(which normally cost double while in your astral stance). But overall the class will play fairly similar to how it did before, the rhythm is just a little changed since you no longer need to refresh Eno. You should pick it back up pretty quick.
And beyond that, just keep pushing the MSQ. If you work at it, youll get up to speed with your gear and play before you reach any instances were your lower levels are a severe hindrance. The game will only force you to get to i230 before progressing into level 61 content, but 260+ is advisable because in those higher level dungeons you(and your groups) will notice the difference. Best of luck!