First of all, the recommended gas to send any ERC20/eth token is 8gwei, but it also mainly affected by the ETH network. When the network is busy filled with so many transaction the price of ethereum gas to send your token will be increased. To make sure your transaction is sent successfully, refer to http://ethgasstation.info to check the currently recommended gas. On the other hand, if you use wallet such as myetherwallet, usually their default gas is already meet the currently recommended gas.