I've been on a 20 year Margarita & fajita safari and had many messican cantina's as customers.
Every one has a different formula, and it varies from batch to batch.
Find one you like and go in enough to become a regular, they will probably give you the recipe, or at least the seasonings.

I buy buy some bulk food from my favorite restraunt, 150 lbs of rice & beans was less than $80.00 last month.