Final answer:
In a mobile-first design approach, performance optimization, the completeness of content, and utilization of touch screen gestures are key factors to consider.
Step-by-step explanation:
When designing with a mobile-first approach, all of the following should be considered: Performance, avoiding content loss, and Leveraging touch screen gestures. Ensuring the performance is optimized for mobile devices entails minimizing load times and making efficient use of mobile data. It is also crucial to avoid content loss, ensuring that the mobile experience is as rich and informative as the desktop version, and to leverage touch screen gestures, which can provide an intuitive and enhanced user experience tailored to mobile device capabilities.