You need to give yourself at least a year on finasteride to see how it's working and if it halts hair loss or even regrows some hair.
Take pictures every couple of months so you can compare.
Realistically you need to hold off until 25 for transplants so that you can gauge how well finasteride is working and what your pattern is if it's progressing.
I know that's frustrating, I started receding at 18, got on finasteride at 21, which kept me from progressing past a Norwood 3A, then at 26 i got my first transplant.
I'm now 34, and after three transplants look 26...and probably looked 34 at 26 prior to the procedures when I wasn't wearing a hat.
This is a long term game plan, you gotta think big picture, there will be no instant gratification unfortunately.
So hang in there, stay positive, do your home work, and get on finasteride.
That's step number one.