Yes indeed you can not just get an Epic card, but unless you have coins !!!
The first one is for sure you should join a clan, which is important in the clan are numerous and active players are requesting cards for upgrade purposes.
Doing donate will give you 5 coin and 1 exp, you can donate up to two common cards in each player are requesting, and you get a 10 coin and 2 exp.
Donate rare cards will give you a 50 coin! Yes 50 coin and 5 exp. But the problem is what if we run out of cards to in donate? Do not worry because there are ways to go about it is by cooperation with members of the clan. Get a friend to donate clan troops back to you that you had donate, so both sides are equally benefited, has not it ??
Another way to get a coin is always logged on all day. Battle, battle and continued to battle, in this way you will get the chest. Gold can be obtained in the chest range from 30 up to 5700 coins !!!
More trophy you have, the more gold you will be.
Login throughout the day? Yes, because every 4 hours you get a chest containing 30 gold coins, so if one day: 24 hours: 4 hours = 6 chest, with a total of 180 gold, in addition to if you got the Crown Chest you will get an extra 140 and 300 gold coins.
Just a reminder that card will be updated every day at the store except Sunday. On the day of the week in the store will be filled with cards on Saturday plus three random cards. In essence, the more cards you donate, the more gold you can, but remember there is a limit to donate is 60.