Limit orders placed on the mobile app will be subject to a flat fee of 1.49% of the order value. For example, if you set a limit buy order for a total of $100 you will be charged a fee of $1.49. There is no convenience fee charge for mobile limit orders.
Limit orders placed via ActiveTrader will be subject to the ActiveTrader fee schedule which depends upon your trailing 30-day trade volume. All Gemini fees can be viewed here.