Foods- there are many type food available, to start you might want to, once you can spare a little gil, and you start to skill up your jobs more, buy crab sushi by the stack(12) for about 4-5k a stack from the AH (auction house under: Food » Meals » seafood), this gives about +10accuracy (acc), if you are going to skill up and your confident that you will not die, buy a marinara pizza (auction house under: Food » Meals » Breads & Rice) this is the best acc and attack food for the price. Later on, when you are closer to your weapon skill cap and want to do more damage, buy cheap attack foods such as Meat Mithkabob ( Food » Meals » Meat & Eggs). Eventually you can buy better, more expensive attack food, eventually.

Rank- Each nation has up to rank 10 mission, the higher the mission the longer signet lasts, and the more access you get to some things such as dynamis. (need be on mission 6+ to access dynamis) Also, each mission rewards you with some gil, more for the higher missions. Check wiki, some can be skipped by trading crystals to the signet npc in your home nation/jueno) and most expect the early ones can only be flagged (flagged- term used to denote availablity of a quest) after trading a certain amount of crystals to the signet npc (check wiki, each mission requires a specific amount).

COP (chains of promathia) - Once you get your 90+ job and 49+ sub job leveled, skilled, and somewhat geared, or sooner, check out the wiki and look at COP. This quest line will reward you with one of the, if not the best, dd ring in the game, the rajas ring and sea access after 8-1. While tamas ring (you may only get one or the other or the long forgotten tanking ring, not worth it personally) was useful at one point, this author feels that this ring, tamas, can be replaced by alternative gear. While the replacements won't be as good as tamas, nothing gets the job done for a dd like rajas, and SE has stated that rajas will get a 99 level facelift, so expect this ring to once again come out on top.

WOTG (wings of the goddess) starting the first questgives shadowreign access (past). a note to you, when you go through a maw in the past always come back through to the present immediately, this will unlock the maw on both sides for you. If you fail to do so and die, you are not gonna be able to access the past again unless you have access somewhere else via another maw you opened in the past or going thru the gates in garlaige citadel which is a SOB. In other words, your first maw is the only time you can go thru the present to the past without going thru the past first, after that ALL maws in the present become locked and you HAVE to go thru the maws in the past individually to access to unlock them for use in the present. completion of the WOTG missions and quests (it's confusing at first, you need do both nation quests and missions to progress) grants some items (depends on which nation you choose to be allied with in the past, you can do all three eventually) and a moonshade earring with varrying augments on it, some are either latent refresh (mp restores 1mp/tic with weapon not drawn) or latent regain (tp restores at 1tp/tic with weapon drawn), as well as several others.

ZM (zilart missions or rise of the zilart) grants sky access and if you do DM (divine might) instead of mission zm14, you can get a decent earring. Pull up DM and see for yourself. the suppanomimi earring is a good one.

Quest- Apoc nigh - need have completed all ZM and COP as well as Bv1 (bahahumat, i botched the spelling I think, first fight) and another quest to gain access to this final fight and it's earring rewards. Ethereal earring is a decent pick.

there's also the add on's and there respective gear for completetion, type ASA, ACP, and AMK for the list of missions and goto the end to see the gear with it's augments you may choose. Again, the COP ring is probably the best item, but other add-ons are still decent, depends on the time you wish to invest in these rewards. There's a few add-ons I left out, mythic ws from nyzul isle, and the TOAU quests, mercanary rank, assualts, salvage, einherjar, limbus, and more. Interested? Check em out.