Notes

MILITARY (300G) - You can upgrade your military each turn for 300G. Each 5 levels, all of your units will get +1 to all stats
DIPLOMACY (250G) - You can upgrade your diplomacy each turn for 250G. Raising your diplomacy will provide you more gold from trade
agreements, you will have higher chance that country (AI only) will accept your trade agreement. Also incrases chance that AI country will accept
your ally or non-agression offer. On level 5 you can rename your state (for example Novgorod Republic>Russian Empire).
ADMINISTRATIVE (400G) - Upgrading administrative will keep your National Unity high, it means no rebellions or uprisings against you
NATIONAL UNITY - You cant improve your national unity directly, but with investing into administrative. Too many lost wars and enemy rebels sent to your country can decrease your national unity.
National Unity - 60% - Minorities will fight for their language to become official
National Unity - 40% - Minorities will fight for their authonomy
National Unity -20% - Minorities will fight for their independence
National Unity - 0% - Your country will collapse, all of the minorities will declare independence and war to you
ECONOMY (300G) - You can upgrade your economy each three turns for 300G. Upgrading economy will grant you +100 bonus G each turn


BULDINGS:

Barracks (800G) - Each regiment of Swordsmans, Archers and Crossbowmans will be duplicated
Stable (1000G) - Allows you to train Heavy Cavalry, also each Light Cavalry regiment you train will be duplicated
Shipyard (400G) - Allows you to build ships
Workshop (1000G) - Allows you to build siege weapons
Market (300G) - With each market built, you can create trade agreement with one bonus country (3 countries + 1 for each Market level)

TRADE:

You can ask any country for trade agreement (Not everyone will agree with it). Creating trade agreement will provide both countries +50G each turn. You can only create 3 trade agreements + 1 for each level of Market

CAPITAL CITIES:

They are heart of your empire and they must be strong! You can build some building to improve your's capital city strength. If enemy win siege of your capital city, your country will surrender and you are probably out of game. Each capital city has 3/10 strenght without any upgrades.
Watch Tower (100G) - You can build Watch Tower in your capital city only once. Provides +1 strength
Moat (250G) - You can create Moat around your city. Provides + 1 strength
Fortress (500G) - Provides + 2 strength. Can be built only once
Walls (1000G) - Provides + 3 strength. Can be built only once

Building all of upgrades for capital city will increase its strenght to maximum, 10/10.

PRICES:
Swordsman - 50G per regiment, 1/1/0
Archer - 75G per regiment, 2/1/0
Crossbowman - 75G per regiment, 1/2/0
Light Cavalry - 200G per regiment, 4/1/0
Heavy Cavalry - 200G per regiment, 1/4/0
Catapult - 500G per 1, 4/0/4
Battering Ram - 500G per 1, only usable against city walls
Transport Ship - 100G, can carry max 30 units
War Ship - 750G, can sink enemy transports and war ships