City Building Strategy

Increasing the number and level of Barracks will increase the speed of training troops.
Building 12 barracks will train faster than 11. Building all level 9 barracks will train faster than all level 8.

Increasing the number and level of Houses will increase population
To grow might faster, you need to avoid having empty training queues. Balancing the speed of building troops against how often you have to train is the key.

If you increase barracks and decrease houses you will train in small batches and have to log in many times a day to avoid an empty queue  = zero training speed :-(    If you can keep up with the speed of training this is the fastest way to grow might.

If you build more houses and have fewer barracks, you will be able to train more troops at a time, and log in fewer times. Your training will be somewhat slower (fewer barracks) but you should be able to keep your training queue from being empty.

Each building has a purpose, and some are optional

 * Watch Tower - You should have one in a city you may open, otherwise it's optional
 * Vault - Optional, but very useful to protect res needed to train with
 * Tavern - Optional, but speeds up res and rein to other members
 * Embassy - One is required to be in an alliance, but others only needed if you plan to ask for reins.  If you built a second one and want to destroy one, you need to drop out of the alliance first, destroy the extra and re-join alli.
 * Forge, Armory, Stables - Each one lets you train t2/t3 troops, and Amrory is required to upgrade your wall.
 * Forge speeds and enables t2/t3 foot troops
 * Armory speeds and enables t2/t3 ranged
 * Stables speeds and enables t2/t3 mounted
 * Keep, Great Hall, Muster Field, wall - keep them :-) and level them up.