Usually the best place to start for any treatment is with your primary care doctor. It is best to have a good relationship with your primary care doctor and you can listen to his or hers recommendations and see how you proceed.
If you are not satisfied or would just prefer to see a specialist, you can see a specialist for high blood pressure which is usually either a cardiologist or a nephrologist (a kidney specialist). Both of these specialist work primarily with disease processes that control and affect the blood pressure and are familiar with the necessary work up to be done on each individual patient and are very familiar with the medications that would be the most appropriate to use.
Again, my first recommendation is to start with your primary care doctor but if necessary to see a specialist, it would be best to choose either a cardiologist or a nephrologist.