In case you become a member and finish quests you are going to earn various gemstones reward. So complete as many guest and battles as you can for many more rare resources.
Experience
Always try to keep collecting from your resource buildings before they are full to gain Experience that is the same amount of Experience whether they have 2 resources or 300 resources.
Quests
When you join and complete quests you will earn as a reward upon completion resources such as the different gemstones. The more battles and quests completed the better chance you will have of collecting rare resources.