If you are in need of more gems to finish upgrades or buy items in Clash of Clans, the only authorised way to buy gems is through the in-game shop which runs via iTunes and Google Play.
There are several third party websites that offer in-game currency for Clash of Clans, but
none of these are safe to use or authorised by Supercell. Often these third parties will ask for your Game Center or Google Play log-in credentials. This means they will be able to access your game, and we can no longer guarantee the security of your account.
In case you purchased gems from somewhere other than through the game, we unfortunately cannot assist you any further as your account is already in breach of our Terms of Service. We reserve the right to ban game accounts with gem orders from third-party websites.