I believe that starting hair transplants at your age maybe a mistake. Many patients do not want to take propecia, however, the side effects are minimal and the benefits are good. You should also consider low level laser(you can purchase a low level laser comb). Many of my patients benefit a lot with this. Platelet rich plasma (cells taken from your blood) injections are also very helpful , especially in the back.
The problem with starting hair transplants at an early age is that hair loss is an ongoing process. We really dont know how agressive your case will be, or how many grafts you will need for an acceptable result over the next 10 years or so. It would all depend on how stable your current pattern is (Its not stable at your age).