For your first bow, I recommend you get a bow weight that you can draw back and hold at full draw for 3 seconds or so, without struggling, and then rest for a minute or so, and then do the same thing again for 5-10 times, with rests in between each draw.
It is good to start out with a light weight bow at first, because you will want to shoot it a lot. I hesitate to say what a light weight bow is, because it will vary from person to person, but for me it would be about 45#. If you want to go to a heavier weight bow for hunting, you will find at first that it is difficult to come to full draw and hold, but your body will adjust, and will learn to pull the heavier weight. But you will never be able to shoot it as many times as you can the lighter weight bow. I can shoot my 65# bow about 10 times before my shooting falls apart, but that's okay for hunting, where you probably only get one shot anyway.