As you are new to the game, building is not a good option. If you can farm npc's, then you can capture up to a lv5 npc with no loss of troops. These can be used as temporary city's until you are ready for something better.
You will need other npc's around that location for farming or open flats so that you can build your own npc's.
The eventual goal is to capture a lv10 npc to convert or capture someone else's city that is better than the city or city's you already have.