In the beginning, you are protected from attack for three (3) days. (You should verify this by going to the Worlds screen and tapping "Info". You should see "Beginnner's Protection" and the amount of time you are protected.)

Therefore, it makes sense to spend your immediate efforts on building your resources: Lumber, Clay and Iron. Take advantage of the Quests, but don't focus on taking any buildings past Level 5 for now, except for your Lumbermill, Quarry and Ironmine. The higher the level of those resource buildings, the faster they will produce resources. As necessary, upgrade your Warehouse; however, you shouldn't have too much to store since you will be spending your resources as fast as you can produce them. You want resources coming in as fast as you can. Then, before the three days' protection is up, you can decide whether to focus on developing an army or building your defenses.