Regarding the economy:
There are still many profitable trade routes. The primary ones I use:
Maidenpool to literally everywhere - Gold Chalices
Draconys, Norvos, White Harbor, and Weeping Town to Kayce or Hull - Jars of Oil
More than half of the cities in the game to Stoney Sept, Maidenpool, Lannisport - Tools
Norvos and Planky Town to Hull - Iron Bars
Just go to any market and assess the local prices with Maron in your party, he starts at Trade level 4. Find anything with a greater expected margin than a couple hundred coins, and buy the higher quality versions of that item. Don't sell or buy too much at a time, as transactions temporarily warp the price of goods. Profit. It may not be as cut and dried as "Buy a ton of salt at Saltpans, sell it everywhere" but it gets the job done.
By the way, what do you guys think about the Riverlands Troop Tree having only 1 tier of archers? I have never personally tested them. Are they good enough to fill their role?
Even elite crossbowmen struggle to get results against anything but the lightest armored of units, since crossbow attack power does not scale with character stats.
Basically, if it's called Crossbowman or Archer, I don't believe in the efficiency of the unit. Once archers become Longbowmen, you start getting good value. I'd rather have a base level Longbowman than an elite Archer (like Dragonstone's forces have). Crossbows are only good if you can't spend the stats on a hero for Power Draw or Throw, I see no reason beyond flavor/lore to take troops with those weapons in your army. The discrepancy in power becomes extremely apparent during sieges, where 300 elite archers inside a castle would be terrifying (depending on the structure of the scene) while 300 elite crossbowmen would just mean that a bunch of spawns would be taken by units that didn't pull their weight, making it easier to get inside the walls.
I haven't gone into many of the troop trees, but I suspect that The Westerlands has the best setup if you don't mix and match. Stormlands is pretty cool but doesn't have an elite tier longbowmen. Riverlands, Reach, and Vale are underwhelming because of the Xbows, haven't messed with the North, Iron Islands, or Dorne too much. Dragonstone suffers in ranged combat but their halberdiers are absolutely nuts and get great value in both sieges and in the field- they don't have shields, but you better hope you kill them before they get to you, and they chop up cavalry like it's nothing.
The "Masterwork" prefix on trade goods gives less of a price multiplier than the "Well Made" prefix.