It depends on how much follow up work you do. If you spend the money for the private lesson, then buy another lesson but haven't taken the time to improve on the things you can, it's not worth it. No point in paying someone to teach you the same things twice.
I would start with 1 private lesson a week, and take some time at home to practice what you learned in the lesson. Combine that with your regular practice where you can apply these lessons and I think you'll have a winning combination. If you learn what you're trying to learn in the private lessons more quickly, then maybe 2 lesson a week would be better.