Here are the most important steps in putting together a guild:
Start it as a group endeavor. Form it up mostly with people that you know and that you know will talk with you on things.
Start a discussion thread based on that discussion...somewhere. Wherever it is most pertinent to do so. Within this thread, do your fund raising. 20,000 gold isn't such a huge number when you split it between a few people. Hell, posting actively and doing Daily Chance for a week will put you near the halfway mark.
Once you have the funds and the plan, create the guild.
Keep the guild active! I'm sure there's a tutorial on that somewhere in the Resources subforum.
That said, I have a now inactive guild in my possession that I'm looking to sell. PM me if you're interested.