Tier 0 - Preparation & Requirements
-Finish Your Job/Story Quests - Your Job quests will net you your last skills and your Artifact gear. Do them. Main quest completion at least through Praetorium is required for literally every piece of content outside of this tier, and many later on will require completion beyond that.
-Replace Your Trash Items - If you have any items below iLevel 45, they should probably be replaced with crafted/purchased items. You should pay particular attention to your weaponry. You can jump up as high as item level 90, depending on how much gil you have/are willing to spend, but bare minimum in all slots should be i45+.
-Castrum Meridianum and The Praetorium - You'll need to run them once for story. If you feel uncomfortable with the idea of 8 man content you can run them once or twice extra, but you should otherwise avoid them outside of Duty Roulette: Story Mode, which unlocks after completing them both, as the base Mythology reward is rather low for their time investment.
-Wanderer's Palace and Amdapor Keep - You'll have to do at least AK for your Relic quest eventually, but they also drop iLevel 55 gear to get you started, and are an easy completion even in fresh 50 gear. They should help ease you into the idea of 4 man dungeons at level 50, and how various classes perform with their full skill set.
-Cross Class Skills - Every Job is a little different on how much they depend on cross-class skills, but at absolute minimum, by the time you reach Tier 2 you should have access to all of the Cross-Class skills considered even moderately useful for your Job.
Tier 1 - The First Steps
-Expectations - Beyond this point you should have Praetorium completed, and a basic set of gear in the iLevel range of 45-55 or higher. Gear from content in this range is iLevel 60-80.
-Relic Quest Line - One of the first stops for a fresh 50 should be picking up your Relic Quest line. Even if you don't want to take it all the way to Novus, it's a good way to jump up into the i80-90 weaponry tier relatively quickly.
-Big 3 HM Primals - Ifrit, Garuda, and Titan HM will all be required of you for a number of unlocks, and completion of your Relic quest. Go bang them out in an afternoon. With big Echo bonuses, and propensity for higher iLevel/experience players to join you via Duty Roulette: Trials, none of these save perhaps Titan should present you with any terrible difficulty. The Big 3 HM Primals must be completed to gain access to The Binding Coil of Bahamut later on.
-Main Story Continuation/Secondary HM Primals - Continue working on your post-Praetorium Story and you'll eventually run into Moogle Mog, Leviathan, and Ramuh HM. You'll need them all dead and the story wrapped up all the way to its current 2.3 completion eventually for unlocks, and Moggle can drop silly i75 weapons for the Moogle addicted.
-Gilgamesh - A for-fun/no-rewards fight in the Hildebrand Storyline; required if you want to unlock Duty Roulette: Trials. Should be no difficulty at any iLevel.
-Pharos Sirius and Haukke/Copperbell HM - These four man dungeons should present you no particular difficulties even at an average iLevel of 55-60, assuming some of your other party members are above that level. You should be going through each four man dungeon at least once so that you can unlock Duty Roulette: Hard Mode.
-Lost City of Amdapor and Brayflox/Halatali HM - Same as above, only with a slightly higher difficulty curve, aim for iLevel 60-70 before jumping in them. Brayflox HM will likely be many people's first experience with the dungeon speed running mentality, so be prepared for much bigger pulls than you're used to. Once you have completed all the dungeons listed to this point at least once you will gain access to Duty Roulette: Hard Mode.
-Labyrinth of the Ancients - The first Crystal Tower/24 man, you'll need it completed for unlock status later for the second zone, and it drops i80 gear with no loot restriction.
-Hunts - You should now be able to unlock the Hunts system, which allows you to reap great rewards from overworld Notorious Monsters. Unlock this as soon as possible and get into a Hunts Linkshell or a larger FC if this is something that interests you.
-Mythic Armor - You should be able to purchase at least a few pieces of Mythic armor either with Mythology tomes, or Hunt Marks. This should help boost your iLevel rapidly. If you have enough Soldiery Tomes you can also begin purchasing iLevel 100 Weathered gear with them.
-PvP & Frontlines - You should now be able to unlock Frontlines PvP and level 50 Arena mode PvP. Frontlines can be a great way to acquire Tomestones and PvP exp while having fun, as long as you can deal with the Frontlines queue insanity.
-Side-Stories - You should now also have access to start the Hildebrand, Courrier, and Winebauds series of Sidequests. These provide various small item rewards, and can be a lot of silly fun.
-Other Unlocks - There are many small system related unlocks at level 50, from Glamours and Personal Rooms to Chocobo Raising, Parley, and more. Keep an eye out for any odd Level 50 quests in zones you walk through, or people chatting about systems you don't recognize.
Tier 2 - Beyond Your First Relic - The Beginnings of the Difficulty Curve.
-Expectations - By this point you should be in the ilevel ~70+ range, with a weapon at least at iLevel 80. Content in this tier provides gear in the range of i80-i100. Content from this point onward will begin sharply spiking up in difficulty, both in terms of numerical requirements and mechanical prowess.
-Hullbreaker Isle and Tam Tara/Stone Vigil HM - These three dungeons constitute the Duty Roulette: Expert block currently. Clear them each at least once, or farm them if that's your preferred method of i80 acquisition and Soldiery farming.
-Ballad: Ultima - At this point, Ultima most likely will provide little that will be of use to you, but if you want to clear him once for fun, or really need an i80 neck piece, Minstrel's Ballad: Ultima's Bane is there. A clear on this is eventually required for Savage Mode Second Coil, far down the line, should you get to that point.
-Big 3 EX Primals - Garuda, Titan, and Ifrit EX are one of many paths to an i90 weapon and i90 accessories. They have been dropped as requirements for other content, so if you don't feel like you need more i90 gear, or are struggling to complete some of these, it is now possible to skip over them.
-The Binding Coil of Bahamut - The biggest method to farm up i90-95 gear at this point, the original Binding Coil will provide you with your first taste of Premier 8 man content, albeit with a very generous Echo buff and a few nerfs to the numbers and mechanics of the fights. Completion of Turn 5 is required for access to the Second Coil of Bahamut.
-Leviathan and Moggle Mog EX - These two are required for Ramuh EX down the line, and can provide you with i95/i100 gear, including weaponry. Both have had progressive Echo added in 2.3, which should make clearing and farming them easy enough to let them drop down a tier.
-Syrcus Tower - The second Crystal Tower/24 man instance. This will get you access to a single i100 drop per week, or an Oil of Time/Unidentified Allagan Tomestone for access to an i110 accessory upgrade or i100 weapon purchase.
-Relic Zenith/Animus/Novus - The long path of upgrading your relic. None of the steps require clearing any of the harder content, and are more focused on simple grinding. If that sounds like something that would appeal to you, this can be a path to a long term best-in-slot weapon for many classes.
-Weathered Gear - Keep capping your Soldiery weekly, and use those tomes to Acquire Weathered Gear. Upgrading these pieces requires Sands/Oils of time, which can be acquired via Syrcus Tower, Hunts, and Second Coil.
Tier 3 - Turn 5 and Beyond - The True End-Game
-Expectations - By this point you should have completed Turn 5 or be actively working on it. Content from here on out will drop all pretenses of the Echo buff and require you to actively work on your skills and gear to make the cut. A minimum iLevel of 90 in all slots should be considered for the following content. The below content provides rewards in the i100-115 range.
-Ramuh EX - Another source of i100 weapons, and i100 rings. A challenging but readily beatable fight. Can save you some Soldiery or help smooth out bad drop luck from Second Coil.
-The Second Coil of Bahamut - The real heart of End Game content currently. Four turns, four bosses, and a whole lot of suffering. Expect to need a static group, and/or a whole mountain of dedication to clear the turns. Drops i110 gear, i110 upgrade items, and the coveted i115 weapons from the final turn. Turn 4 completion is required for access to Savage mode.
Tier 4 - For the Brave
-Expectations - In order to tackle the content in this tier, you must have completed both Second Coil Turn 4 and Ballad: Ultima. Your gear should all be i110+ or close to it. Content in this tier is purely for bragging rights/titles, and not for the feint of heart or easily enraged.
-The Second Coil of Bahamut (Savage) - The insane man's version of the Second Coil. Provides no added benefits other than a title for each turn cleared, at an insane difficulty spike. Maybe you'll be the first to clear some of these turns?
