With respect to interface, Firefox has been very clear not taking a specific framework to give applications the Firefox OS look&feel. Their strategy is: “Use what you want.” Fortunately the source code of your UI layer (Gaia) is available for beeing used and there are already people who have made little things to help.
I haven’t had much time lately (I’ve been forced to socialize with other human beings), but I had the time to develop an dummy app embedded with the Twitter Search API. I used my favorite stack, ¡Puppeteer! Puppeteer! (udercover advertisement), which continues being a Backbone with Marionette. And I used for the interface what I commented before (Gaia).