Forts are a must have if you can afford them. They increase the time of sieges and make assaults more costly for your enemy - be it a player or rebels. I'd recommend to get tier IV in every province sooner or later.
Military buildings are great. The manpower bonus from tier I will significantly help you in the earlier stages of the game. The higher tier buildings are a bit more situational, so I'd get those for provinces you want to use primarily for recruiting your army.
Tax buildings are always good for more income and better fort/spy defence.
Production buildings are also good, but a bit more situational because they scale a lot with province production values.
Navy buildings are good if you need NF limit or want to boost trade power. Overall they are rather "meh", but getting high tier stuff in a few provinces to build your fleet is always worth it.
Trade buildings are important to dominate your home node. Always get them in provinces with Estuaries or COTs. Ultimately, they should go up anywhere sooner or later, for every ducat you get from a COT is a ducat less your enemy gets.
Unique buildings are costly but worth their money. Get them whenever you can afford them.
Manufactories have high investment cost but offer great benfits on valuable goods.
Military buildings are great. The manpower bonus from tier I will significantly help you in the earlier stages of the game. The higher tier buildings are a bit more situational, so I'd get those for provinces you want to use primarily for recruiting your army.
Tax buildings are always good for more income and better fort/spy defence.
Production buildings are also good, but a bit more situational because they scale a lot with province production values.
Navy buildings are good if you need NF limit or want to boost trade power. Overall they are rather "meh", but getting high tier stuff in a few provinces to build your fleet is always worth it.
Trade buildings are important to dominate your home node. Always get them in provinces with Estuaries or COTs. Ultimately, they should go up anywhere sooner or later, for every ducat you get from a COT is a ducat less your enemy gets.
Unique buildings are costly but worth their money. Get them whenever you can afford them.
Manufactories have high investment cost but offer great benfits on valuable goods.