in my experience, lessons are analogous to rehearsal and the time between them to
practice
in other words, what you do in those 2 weeks between will dictate how well and quickly you learn and progress...i think this is kind of what you are saying, so to answer what to do in the time between, i echo Bill--do what the teacher tells you!
seriously, if the teacher is good, he/she will outline a lesson plan and let you know what to practice for the next lesson, and when the next lesson comes a good teacher will expect you to show that you've done this homework
as an example, you may be asked to construct arpeggios for chord progressions, play these in all positions, play scales in all positions, etc...the kind of thing that we need to know and work on alone anyway--the teacher should be there to guide, answer questions, inform your technique, etc...
can you sight-read? that's definitely something i need to work on moreso than i do, and will open a lot of doors
good luck, wish you the best!