If time is important, you should start immediately one-on-one as you say. My partner and I take two 1 hr lessons a week, practice between 4 and 8 hrs a week. We are looking for a new place to practice and that is why there is such a large spread in practice time. If you plan to compete with a partner, then start when you get one. If your plan is pro-am, save up as it is a costly way to go. Your questions indicate that you are making decisions before you have gotten started. In that case enjoy your group lessons. Time will provide you answers to most of your questions.