Building Up Your Base

Building up your base is a very important activity to improve the hitting power of your team, but it takes time.  To accelerate the process, consider buying a VIP Pass that will provide you with an extra Builder and let you go twice as fast.  BUT, never spend your gems on the speed ups for building completion.  Be patient, save your gems for buying high level heroes at the Summons Gate.

First Priority:
Your ability to level up heroes will be limited (in part) by how much food you can gather.  So you need to build up your Farms.  Building up Farms requires iron from the Mines.  Building up the Mines also requires food.  Leveling up your Farms and Mines must be preceded by leveling up your Stronghold, which requires max'ing out your resource storage.  So these 4 building types should have first priority.
- Level up the Stronghold
- Build new Mines and Iron Storage if you can, and Level up
- Build new Farms and Food Storage if you can, and Level up
- Level up the Watchtower (which is also a resource gathering device)

As a rule of thumb, finish leveling up the Mines and Farms and Storage as far as you can, before leveling up the Stronghold again.  Leveling up other buildings will generally require that you have max storage for resources.

Second Priority:
The other thing that limits the rate at which you can level up your 4* and 5* heroes is the quantity of lower level heroes you can gather.  So your second building priority is to create and level up the Houses and Training grounds with which you can generate and store lots of 1* and 2* hero fodder for your leveling actions.  You want to get multiple Training grounds to Level 11, where you can churn out lots of low level characters for lowest cost.

Third Priority:
You still need to build and level up the Barracks and the Crafting buildings, but these are not as crucial as the others.  They can lag behind somewhat, until later when the farms and mines are cranking out the supplies.