You don't need to build B2G on your own. The only thing you need to try things out is the Firefox OS Simulator extension available at: https://addons.mozilla.org/en-US/firefox/addon/firefox-os-si... this works only on Firefox of course.
I wrote a free quick guide for developing apps for Firefox OS that walks you through this steps, you can fetch it in EPUB, PDF and MOBI from: https://leanpub.com/quickguidefirefoxosdevelopment/
Feel free to reach out for us if you need anything.
PS: I am a Mozilla Rep.
You don't need to build B2G on your own. The only thing you need to try things out is the Firefox OS Simulator extension available at: https://addons.mozilla.org/en-US/firefox/addon/firefox-os-si... this works only on Firefox of course.
I wrote a free quick guide for developing apps for Firefox OS that walks you through this steps, you can fetch it in EPUB, PDF and MOBI from: https://leanpub.com/quickguidefirefoxosdevelopment/
Feel free to reach out for us if you need anything.
PS: I am a Mozilla Rep.