There are only five types of troops (Archers, Cavalry, Infantry, Catapult and Carts). Carts are for carrying resources, while the other four troops are for fighting. With so few troops, winning battles against others is entirely a numbers game. So to win, get as many resources as possible, as quickly as possible, and use them to train as many troops as possible.
The simplest way to increase your resource numbers is to level up your Iron Mine (for iron), Stone Quarry (for stone) and Woodcutter (for wood). Each one of these buildings produces resources on an hourly basis, and every time that you level these buildings up, you’ll increase the amount of resources that they earn per hour.
Raid other kingdoms and figure out which ones make for easy resource gains. Be sure to take plenty of carts with you (you need the market to train carts) so that you can carry back a large quantity of resources at one time. Abandoned settlements (owned by players who no longer play) are the best for resources, because they are completely unprotected yet they continue to produce resources.
Many heroes will provide resource boosts if you make them the mayor of your town. Possibilities for special abilities include stone production, wood production, iron production, or storage space. Use silver to level up your heroes in order to increase the size of the bonuses.
There is only one way to get more food, and that is by upgrading your farm. Food is not produced in the same way that wood, stone and iron are. Instead, there is a set amount of food, and a “over-under” number. If your troops are not well fed enough, then the food number will be negative or 0. If the food number is positive (has a plus sign next to it), you have enough food. Upgrade your farm to get back in the positives.
There are a couple of ways to get silver. Silver can be earned as a reward for completing quests, or (more frequently) as a reward for leveling up. Otherwise, a good way to earn silver is to kidnap another player’s hero, and then hold the hero in the City Guard cells for ransom. The other player will have to pay you silver in order for you to free the hero, so kidnap an active player’s hero.