Improve your base early in the game. Build all possible structures and upgrade them as often as possible. The single player campaign can become difficult quickly. Only attempt conquering other bases after your own base is set up properly. Use the free time boost that becomes available after there are five or less minutes of building time whenever possible. Defending your base is best done through proper design. It will not be possible to have everything protected by walls and defensive buildings. Instead, position defensive buildings around your Town Center and surround them with walls to allow them to stand longer. Keep the resource buildings within sight to bait your enemy. An opponent cannot use the target too many times in battle. Try to reach to the Medieval Age as fast as possible to have gain more defensive options. Build them first and only upgrade them afterwards. Towers that are under an upgrade will not provide their bonuses if you get attacked. Try to time upgrades when you have a peace treaty.
Battles
Consider battling for resources and not for victory. The more medals you win, the more difficult your opponents will become, and you will attract the attention of more powerful enemy civilizations. Try to keep your medal count low for as long as possible to allow you enough time to build a stable civilization.
Gold
At first, you can earn gold by hunting rabbits and foxes. Later, get the gold from the mine to connecting as many of your buildings as possible to the Town Center. This will allow you to earn free coins easily. Trade at the market when notice that it is full. Sell the items that you collected by performing the tasks at the civilization screen.
Layout
Remove the forests whenever possible to gain additional space for expanding your civilization and building your base. This also results in finding various items.
Workers
Always keep your workers busy. Have them building, upgrading or collecting something. Manage your workers to maximize your revenue, especially early in the game. Upgrades and buildings require a lot of time. Instead of focusing on those tasks when first starting, have your workers hunt, harvest and collect as much possible. Only begin upgrades or building before you log out.