What a wonderful response, Core.
OP, Core is dead on in her response. Dressage isn't something that you just pick up and dabble with in the arena on your own. It is often incredibly difficult and requires a huge degree of self discipline, focus, determination and sheer grit.
If you want to ride walk, trot, canter and a bit of leg yield, then that is more along the lines of basic riding than it is Dressage. Dressage as an art, in it's true form is something that it's 'lovers' will work and build of for a lifetime, and still be a beginner in the sense of how much their is to know.
After riding for 20+ years, I am only now just beginning to understand and feel true collection. I've had a basic grasp of it, of the concept and how to train towards it, but every time you feel like you've fully grasped a concept, you have a lesson and realise that you have really only just tapped into the tip of the iceberg.