FoxBox is the project that intent to provide a battery included Firefox OS build environment.
It will be great to setup the current version of foxbox in your desktop environment
And record obstacles you encountered here https://github.com/gasolin/foxbox/issues?state=open. There are some issues (but not the limit) that might be worth to do in the future version of foxbox.
Note that you require a desktop with INTEL VT-x/AMD-V hardware virtualization support(Windows8 or Mac already enabled it), at least 4GB RAM and about 10~40GB disk space(for gaia or full B2G development).
FoxBox has been approved by the Google Summer of Code administrator http://wiki.mozilla.org/Community:SummerOfCode14 , so its perfect time to step up, try FoxBox, fix issues that every others will encounter, save everybody's time and start make your own Firefox OS phone.
If you'd like to contribute FoxBox for SummerOfCode14. We expect you could find out the interesting topic you want to contribute or any other way that can better achieve FoxBox's goal.