I thought I'd give some hints on Ambition Mode that I learned playing the JP version. This would've helped me when I first started out. :)
In Ambition Mode, weapon materials are more important than building materials in the long run. The number of buildings are limited, whereas weapons can be infinite. There are 8 buildings and 288 materials required to max out one building, so 2304 building materials are needed in total. To contrast, I've used over 10,000 weapon materials in my game forging optimal weapons for every character.
Starting off in Ambition Mode will be a grind, so it's important to level up the right buildings to maximize efficiency. The best buildings to max out in order are: 1. Dispatching Post (not sure of the English name; you pay money to send troops on a mission and claim rewards) - focus on locations that reward you with weapon materials (they alternate between building and weapon materials). Once maxed out, the last location can reward you with up to 16 weapon materials and up to a level 4 weapon for a 10,000 gold investment.
2. Stable - feeding the animals will always give you weapon/building materials, and a bonus animal or weapon.
3. Farm - assigning a general here will sometimes reward you with materials. The farmer NPC will also give you gold for free when you talk to him after battle. I find that if a general doesn't give you materials after a few attempts, I switch to another one. I also always switched generals after receiving materials.
The rest of the buildings can be leveled in whatever order you prefer, but DO NOT max out your trading post. From levels 1-49, the trading post will allow you to trade 1 weapon material for 2 building materials. Gather weapon materials as much as possible to take advantage of the 2:1 trading option. This will allow you to level up your buildings quickly.
Continue to level up the rest of your buildings, but leave your trading post ONE material away from maxing out. Continue to gather weapon materials and trade into building materials. Once you've maxed out your building materials (9999), spend one building material to max out your trading post, which will also trigger the completion of the palace.
With all buildings now maxed out, building materials are useless, but the level 50 trading post will now trade 1:1 between materials. Trade your building materials to weapon materials as you please. You can also continue to gather building or weapon materials. It doesn't matter which type now because they're essentially the same with the trading post.
Maxing out an optimal weapon with all level 10 skills can be done for about 150 weapon materials or much less if done efficiently. I've done this with all 77 characters and still have plenty of materials to spare.
As a follow up, in the JP version, if you play an Ambition Mode battle and return to the host's town, you can use his facilities. This means someone with a maxed out trading post can go back and use the 2:1 ratio if the host hasn't maxed out his trading post. The trick went like this: - trade all building materials to weapon materials - participate in battle and return to host's town - trade weapon materials to building materials up to 9999 - return to own game and trade back to weapon
This means an easy way to double weapon materials at anytime, but it requires coordination with another person playing the game.