For those who do not know, Diplomacy is a mini-game using cards and skills. The best way to learn it is to do the in-game tutorial quest. And make sure you do both the general diplo one and the civic one. It doesn't matter if you do the quests in your home town or one of the other starting areas or even major towns. I did mine in Lomshir because everyone was close together.
There are a LOT of low-level quests on Qalia for gear. I've also seen a lot of quests on both Thestra and Kojan, including one on Kojan for a diplo pouch that lets you carry diplo items in a different pouch (like a crafting bag).
When you do parleys (the mini-game with npcs), there is a note on each as to what skill they use (noble, academic, etc.) and the required level. You can get skill through items since almost all of them give you something, like +59 domestic. As noted above, you can also learn skills through civic parleys, but that is SLOW.
The xp curve is steep. Even at level 10, I was getting 30k+ parley xp rewards, and only moving the bar a tad. Doing lvl 20 parleys gives 69k+, and still only moves a tad on the bar. But even so, parley xp is faster and better than quests. You'll need the gear and cards from quests, but the xp is better from civic. You just need to find a good spot where you can go from npc to npc quickly without changing cards to race through the parleys. Khal bar is a good spot for early levels, up to about 22 so far.
Cards can be from quests or from drops now, and the extras can be sold on the broker. You can also get gear from the brokers. Just remember almost everything is BoE now. And you will likely need to carry several changes of diplo cloths for the various types of parleys. So the bag quest is a good start.
We need the following for the quest for the Guild Hall:
100 evidence of arcana - unequalled
100 evidence of trends - essential
100 evidence about plots - crude
100 rumor of blackmail - significant
100 rumor of arcana - vital
100 rumor of trends - unequalled
100 hearsay for blackmail - unequalled
100 hearsay about trends - crude
100 hearsay about arcana - crude
50 shiny prestigeous bauble
100 prestigeous bauble
Not all is tier 5 or even tier 3. Some is tier 1, some 2, some 3, etc. I have seen 3 different rumor of arcana so far, and none of them are the ones needed. I think Hearsay for blackmail is the easiest, followed by the prestigeous bauble. I've found that there are 5 different versions of each. I'll update the list as I find out which is which. The levels are crude, significant, essential, vital, and unequalled (t1 to t5).
From a barkeep, you can get the baubles, expendable buff items (hold in hand for a bonus at the start of the parley), food/ drink, and any of the papers. Civic diplomacy from any of the others could get you a paper. Civic diplomacy can also get you skill advances in the various diplomacy areas, like noble, domestic, etc.
I'll collect up the various items, but not sure yet who will do turnin. The actual plots are not yet in game, but there is a message up that a player/ account cannot own both a personal house and guild hall, so we will need to do some shuffling later. We are still WAY off from the actual Guild Hall, but we are making progress.