Here I will explain all buildings.
This is your castle and represents your level; by upgrading the castle, you can increase the level cap of other buidlings. If you can't level up anymore, it means this is the max cap of your region (It will say: "This building's level has reached its regional cap").You can only reach level 20 if you didn't beat Sphinx yet. After you defeat the boss Sphinx, you will move automatically to the next region with the cap of level 30 (30r).
After defeating Raphael, you are allowed to migrate to next region with the cap of level 40 (40r). Just tap on wold's map, choose the next region, where you can press migrate.
Here: lv. 40 region
Valhalla: Warrior Post
Crusader: Honor Fort
In order to enhance your gears, you have to upgrade this building first. After upgrading the building, you can also get more shop items or flags to buy.
The building will increase the cap of your gold.
ATTENTION: If your gold is above the cap, you will lose it after occuping a goldmine.
Many people have lost over millions of gold because of this issue. So don't occupy a goldmine or you should spend all your gold in first place.
Altar of heroes
Here you can put your heroes in training to make them stronger and for leveling them up.
It is already unlocked if you step into your city for your first time, but you can use it after defeating Orpheus in Ring of Courage.
(half way of the map, after Prometheus)
Put your hero in training. You can choose between 8 hours for gold and 24 hours for 3 rubies.
Notice: Some people choose 24 hours, if they reset their account for daily login because they have to be offline for 24 hours.
If you got higher ViP-Level, you can choose more options.
For example: 72 hours for 30 rubies
You need to buy trainingslots to train more heroes. It's worth buying, so it will be faster to finish training. I can't live without 5 trainingslots :3
You can unlock 3 trainingslots without ViP-Level. The second slot costs 50 rubies and the third one costs 100 rubies.
Notice: You need higher ViP-Level to buy additional slots.
You really should try to upgrade all techs to get better defense or strength.
It will unlock after defeating Liz the Shadow in Ring of Courage (third NPC).
Upgrade your castle to get more techs.
There are many techs: up to lv 40
Leadership Skills - Increases your heroe's units.
Weaponry Expertise - Increases physical power
Toughness - Increases physical resistance
Encouraged Charge - Increases tactical power
Anticipation - Increases tactical resistance
Elemental Mastery - Increases elemental power
Spell Deflection - Increases elemental resistance
after lv 60
Banner of Glory - Increases your heroes' units (double as Leadership)
War Experience - Increases the amount of merits you can gain from NPC
after lv 80
First Aid - Restores part of your fallen units after battles
Mobilization - Increases the efficiency of the enlistment
Reinforcement - Reduces the chance of your buildings to be degraded (doesn't work)
War Machine - Increases your chance to degrade your enemy's buildings (doesn't work)
Tenacity - Increases army's mitigation of all damage
There are formations techs, you need to upgrade for using more heroes in your team.
For using three heroes - Level 10 / tech formation lv. 2
For using four heroes - Level 25 / tech formation lv. 5
For using five heroes - Level 50 / tech formation lv. 10
Five heroes is max you can use for the whole game.
Formations: Aegis, Scimitar, Burnout, Onslaught, Whirlwind, Billow, Thorns, Megalith
My favourite: Aegis, Whirlwind and Billow
The building will increase the cap of grain.
You can occupy the farm for getting more grain.
By upgrading this building, it will increase the amount of enlisting by mobilizise.
Mobilizise is free and you can do it 10 times a day.
Enlisting is to fill up your troops.