• Ruins – Before you can construct a building (or a totem) ruins must be cleared. Ruins of buildings are cleared automatically so you can construct buildings right away. Ruins of totems need to be cleared and it requires resources. Tap on totem ruins to start clearing. 
  Cleared Ruins – After the ruins are cleared, tap the building icon to construct a new building (or a totem). You can play match-3 levels in buildings. In the totems you can get deals on bonuses.
• Locked Building – It means you haven't reached the required XP level to build this building (or totem). The number on the shield shows the required XP level.

You need to have enough resources to clear totem ruins and build buildings. Clearing totem ruins and construction of buildings takes time.You can speed it up using your crystals.