I quote everything of Michael and this is the first point, with the Live coding series on airmo and codefirefox.com that there are for user with skills but not very entry level.
We need something very simple for new volunteers to contribute, once was Firefox OS but now we are in a limbo without news about IoT so actually we have nothing for them.
The triagebot (random ticket to triage) was a cool idea and i contributed in the past but the problems (the reason i removed my participation in that project) was the missing settings to choice the platform to triage the ticket. Maybe we can improve this for that point.
We need something concrete for new volunteers without many development skills, actually I am working for this with the webextensions platform (that can be a way).