HorseRiderLover, how exciting this must be for you!
The height doesn't really matter, but maybe you have ridden several different horses in your lessons that have different heights? If so, then maybe you prefer one of the horse's heights more than the others? I would go for a horse the height of the lesson horse that you like the best.
Also, if you have decided one the height, price range, age, etc. then maybe you can tell us and I can help you out with some online horse shopping!
Hope I helped! :)