You can get more resources in these ways:

Command Center
  1. Build more resource buildings in your Command Center and upgrade them to higher levels. They produce lots of resources.
  2. Use Boost items to increase the production rate of resource buildings.
  3. Activate VIP privileges. The higher you VIP level, the greater production rate bonus your buildings will enjoy.
  4. Use Resource Items in your inventory.
  5. Buy resources in the store.
Battlefield Map
  1. Gather resources. There are many resource plots on the battlefield map. You can send troops there to gather resources.
  2. Plunder resources. There are many enemy Command Centers on the battlefield map. You can send troops to attack them and plunder resources.
Event
  1. You will get rich resources as rewards in many events.
Recharge
  1. Buy packs. It's a very good bargain: you can get tons of resource items in addition to Gold.