As resources are limited at the beginning, it is necessary to make plan and upgrade your Buildings wisely. Here are the three ways of doing it.
Recommended for beginners at strategy games. Finish the main quests and upgrade your Buildings equally. Try to understand how the different Buildings help you and invest more in your favorites in the future.
Good for experienced players. The Buildings that produce resources are the key. Upgrade Farm, Quarry, Iron Mine, Tent etc. to obtain a lot of resources and make that your advantage. The focus is not on gaining power in the beginning but to obtain a lot of resources to surpass your enemies in the future.
This one is recommended for hardcore SLG players. Upgrade mainly Barracks, Technology and Battle Buildings etc. to plunder the resources of your enemies. It is the best strategy for those who want to be very powerful.