As the link from the FAC says, registering an association of any kind, CSC's included, costs about 50€. Requisites are simple, President+Secretary+Treasurer, Statutes that can be copied or adapted, a forwarding address and a few months to wait for the registry to be official. After all, you're only saying you exist. Same goes if you want to set up a "Friends of Satan" society, just don't forget the fifty quid. That's the actual start.
FAC reccomends to avoid paying set up fees to cheeky agencies and doing it yourself, but also FAC is intended for activists and their explanations include things like "combat discriminating government", so... From the bussiness point of view, i know i wouldn't move a finger without a proper legal frame and pragmatic considerations.
A license to operate can be refused after long waiting periods for menial and arguable details. I suppose it's a market built around all that, but i don't have references. Patience unavoidable.
If you know people who are running a successful CSC, your best bet is to copy it from scratch. Broadly speaking, seems that once established is easier to operate if you're a foreigner, that too, but that's just a perception.
Bear in mind that Spain has had close to 25% unemployment and an estimated 3-4 million regular tokers. If there was a guideline, the 1000+ clubs would be 100.000. Something is stopping that to happen.
As for the relevance on which area of Spain you're looking for, (as said, there are significant different approaches from councils), best is to get a local lawyer. Google "cannabis abogados" and there you are, first few ones are from Madrid, BCN and Bilbao. I can't reccomend any in particular.
People have the right to learn through their own mistakes and on the other hand there's always a chance to hit the jackpot, regardless statistics. As you said, some of them seem to be doing pretty well. However, i think a bit like Chaos, so it wouldn't be honest to encourage the idea, but best wishes with it and hope i'm wrong.