Well I am also fairly new and usually don't give out advice because of that, but...
It depends on the style of bow. Pyramid bows are usually the same thickness out of the fades to the tip, this is because of the even tapered limb width from the end of the fades to the tips. This is the style I would suggest for your first bow, and it works great with hickory.
With other designs, such as a parallel limb design, the width of the limbs is the same (parallel) for a set distance (anywhere from 10" from the fades to 6" from the tips)and then tapers to the tips. With this design the thickness of the limbs usually has to taper from out of the fades to the end of the parallel limb section.
Usually with your first bow, longer bows are more forgiving and easier to tiller (maybe start with a 68" bow or so) Be prepared to end up with a lighter bow than you anticipated, it will happen with your first few. If you use hickory, just make sure it is dry.
... again take my advice lightly, I'm sure that the real experts will step in and steer you right