What is the monthly card and how do you use it?

You receive a monthly card either by recharging for 4.99$ 260 diamonds or by buying a gift pack (only able during a special event time) where a monthly card is contained.

You mustn't "use" the card but it is activated as you bought it. One monthly card allows you to receive 60 diamonds everyday for 30 days. If you buy another monthly card within these days another 30 days will be added. for example: 15 days left-> recharging 4.99$ -> now 45 days left. But don't worry, one mustn't overdo with buying those monthly chards since you can also play the game without them or just buy them once or twice a year.