Haven't seen it posted so I figured I would post this here to help anyone (mainly new players) decide which company to focus on. The following companies sell weapons for the following classes:
Maelstrom (Limsa Lominsa)
Marauder
Lancer
Thaumaturge
Twin Adder (Gridania)
Pugilist
Conjurer
Mage-oriented shields
Immortal Flames (Ul'dah)
Archer (+Arrow stacks of 999)
Gladiator
Melee-oriented shields
Yes, I'm surprised most weapons are sold in towns other than their guilds myself but it's the fact haha. All the nations have a few pieces of armor as well for each Disciple type. From looking at the stats of the nation specific (Unique/Exclusive) weapons (one at 30 and one at 50) it does appear that the weapons you can buy in the Market Wards/craft yourself are sometimes better for rank 30 and generally not as good as the purchased ones at 50, though not by much (quite literally +1 in some stats on some pieces while larger on others). The purchased weapons do offer some stat bonuses, too. Good gear for being essentially free and easy to get if you're broke! Feel free to add anything you'd like to this.