I certainly don't have the statistics of successful language educators (language educator = teacher?) with me (nor do I have any idea of what makes a "successful" language educator), but I have met quite a few people who want to speak a language and sit around all day memorizing grammar rules. The problem is that they don't know any words so they can't say anything. So in my original post, I asked what the OP's goal was. What good is it to know how to form certain "cases" if you don't know any words to apply them to?