I second Ben's comments above, and re-emphasize G-Chan's 3rd & 4th points. Someone suggested that YouTube is your friend, but I'd advise against that for your level because there is a lot more tournament-style kendo videos than videos that help you build solid fundamentals. And taking a close heed of the words of your sensei takes the precedence over any observations you make at this point.

Learning kendo or any other martial arts is an interdisciplinary enterprise, and learning solid foundations in building character, spirit, and decorum should go hand in hand with building your physical skills. Meditating on the stated purpose of practicing kendo can also be enlightening.

As for the quickest way to improve yourself in kendo... all I can think of is making every suburi count instead of just doing the motions, and do this at ALL TIMES. At the dojo, I see too many people just doing the motions with no sense of spirit, no sense of seme, no sense of maai--they're just there to swing a stick, or maybe get some exercise moving their arms.