I am an Indian so I could suggest you in Indian structure. when we won gold bars we are so happy just think if you place some small amount in place of gold bars than the happiness is increasing more and try to add chatting to each friend individualy or voice chatting also, so that your player's may increasing. Simply try it then see the magic. I am candy player from last 10 years. This idea working for Indians I don't know for other countries it works or not so if you like my idea then please try once for better results. Thank you