Compress your territory if possible. The more compact your camp, the better. Do not limit the number of buildings you have; simply space them closely together to make your camp easier to defend. You will be able to use defensive walls and towers to easily fortify a smaller camp's perimeters.
Create a guild and get members as soon as possible. This will allow you to assign troops to them through different camps. This is a good way to get experience for new characters. Search the map for an abandoned camp. These are camps that do not have defenses and have not progressed very far, but are still producing resources. Attack abandoned camps and loot all their resources.
Do research as often as possible if you have the resources. The faster you complete your research, the more types of mercenaries and technologies you will have available.
There are four resources that you need to resupply (ore, food, stone and wood). There are resource buildings for each of them (lumber yard, farm, mine, and quarry). These buildings must be upgraded in order for them to store more of their corresponding resource. If a building reaches its storage capacity, it will no longer provide its resource.
As these storage reach their limit, you are not able to generate resources anymore.
When first starting, ignore your offense and defense and focus on your resources. Upgrade everything that affect the regeneration of your resources. You can collect resources frequently and easily when you are actively playing. You will eventually have to upgrade the storage capacity of your resource buildings so you can gather resources while not playing.
If you plan on logging out for an extended time, spend all your resources to prevent them from being stolen by other players stealing all your resources.