I think the mentor system would require the guild to have more features/more complex features. Everything is pretty straightforward already with the different sections, what with all the roleplaying sections having solid explanations on what kind of roleplays go on there. I like the idea of the points system [@SilverRain] had, but bribing people to help almost feels shallow. 

I think online communities are hard to get into- unless you already have friends in that community, it's very difficult to start meeting new people, especially when the only ways to do so is post an introduction thread and hope somebody responds, or join a new or old rp and pray to god you keep interest/it doesn't die after you join/people take enough of an interest in you to actually start a conversation with you.

So what if the mods ran a large game of "You Are Your Avatar" or something similar, for the entire community? Make veteran roleplayers or well-known members of the community sub-GMs if they want the job, and have them encourage new members to join the game and meet some new people. With the entire community invited to come, there's bound to be loads of people for newbies to meet, and since You Are Your Avatar doesn't require a whole lot of thought put into it, I'd say it's a good introduction for newbies into roleplaying.