If production of one mineral or resource grinds to a halt, try stopping production of all other resources by tapping the mines or buildings and then tapping the button with the open hand. This will force the production of your missing resource only. Just don't forget to undo all this later on. Military buildings are useful not just for housing soldiers but also for extending the range of your territory. Build small and medium-sized towers often as you expand and remember to garrison them with a swordsman and two bowmen for the best chance of defending against an attack. Pioneers are useful for sculpting out new territory far from your original encampment. But be careful not to wander to close to the enemy as they will take offense at your expansionism and quickly kill your pioneers.