Man I haven't made a journal in ages, let alone a useful one.
Invite new users with a positive attitude both from the inviter and the invitee.
Set up a "Fair Market" price system, not to bully people into following, but to accept of their own conscience.
Possibilities include: Always selling gold shop items for less than the original price, setting up individual price guides (1 nice background, $x maximum, background set with 4 pieces is then $4x max), some sort of general maximum limit for super rares ($20 mil? Less? More?).
Create new event threads or guilds that welcome everyone in without being too complex. User events could even run alongside major holiday events. Don't want to fight, you want to show off Halloween costumes for prizes, like a Halloween dance - do itttt. A big meetup in the spooky part of zOMG that day? Do itttt.
Be positive, that's the most important thing. Be the change you wish to see.
Offer help if applicable - Forum Assistant, mini contests, hard work in Stein's contests to build new items, welcome the newbies, etc etc etc etc.
(Speaking of that, off to welcome people now...)
Artists who want to just contribute free items, offer work on the manga if they could... That'd be something...