From Dragon Mania Legends Wiki
The only ways to obtain Clan Coins are by participating in Clan Events and completing Clan Quests (between 90 and 130 are awarded per quest). In Clan Events, the coins are rewarded as leaderboard prizes (between 750 and 5,000), given in exchange for duplicated Dragon Pieces of already-owned Clan Dragons (between 50 and 500), and awarded to the MVP of the Clan (between 500 and 3,000). A maximum of 1,000 coins can be obtained from Clan Quests by individual members each day. The limit resets daily at 03:00 UTC.