Any territory can build a palace as long as you have a castle of the appropriate level. 12 Seasons 3000 Koku Citadel Golden Palace Armories Armories are an important part of any territory that can build them. To build an Armory, the territory must have iron sand deposits and a castle but the extra armor bonus will help your troops to stay in battle longer and take fewer casualties. Famous Armory Swordsmiths One of the upgrades to your troops is the event of better weapons. This can increase the efficiency of battle a bit and make a losing battle winnable.
Any territory can build a sword smith if the castle is upgraded enough.
Structures Below is a list of all the structures that can train troops in the game of Shogun. Some require that other buildings or events happen prior to you being able to build them and that is discussed above in detail. This chart will provide you with a quick reference to what each building trains without all the details. There really is no law on what to build because every game is different and your needs will be different. I start with farms and mines if you can build them.