To configure an OpenVox GSM gateway for optimal performance, start by accessing the web interface and updating the firmware to the latest version for enhanced stability and features. Configure the SIM cards, ensuring proper network settings like APN and signal strength optimization. Set up VoIP parameters, including SIP trunks, codecs, and routing rules for seamless integration with your telephony system. Enable advanced features like call failover, SMS routing, and USSD support if required. Regularly monitor performance via the dashboard and logs.