Well you don't have to /shout if every 20 seconds. Just once in a while, while you're in town, toss out a /shout every few minutes or so. As far as people getting sick of hearing about it, there are lots of shouts that I see constantly, tossed up every 20-30 seconds that I get sick of seeing sooner than I get tired of seeing people trying to recruit for a LS.
Casinos, for example, need to die.
Anyway, Gaara, I know a lot of what I've said in posts sounds harsh, but I am trying to help you as well by offering my experiences. I've run RP groups in one form or another (forum, email, text-based, and MMO) for nearly ten years, so I ask that you at least think about some of the things I've said in regard to the difficulty of something like this. I don't -want- to discourage anyone.
But honestly, it's your LS. Get at least one more sack holder, /shout for people once in a while, and take reference from people who've already gone through what you're trying to do. Waiting for other people to do things for you, and then not listening when others try to give you ideas on what works and what doesn't isn't going to get you far.
If you have questions about anything, I'm also Tenshihi in game. Send me a /tell sometime.