The reason to get D5100 and not D3100, is that as your skills grow you will think that you need a "better" camera body very soon. With D5100, you will be happier for longer time
Hi, I was i your shoes not too long ago, and here is what I learned.I would be talking in terms of Nikon, since I know it.try to stretch your budget and get D5100, with the kit lens. And start learning. You would like it, and will learn basics very quickly. After you learn the basics, you will know what additional lens you need. 55-200 is an older lens. 55-300 is the one becoming popular. Now, that is a great lens. But, Think of it as special purpose lens. It will not let you take better shots than 18-55. It will allow you to take shots of subjects further away. If you will think that you need it, get it after you learn the basics. It may happen, that after learning the basics, you will like to do landscape or street photography. And for that reason, 55-300 is not too good. For portraits I would suggest getting "prime" low light lens. 50 or 60mm with maximum aperture at f1.8. Again, once you learn the basics of aperture and general photography, you will know why.
:) It is interesting, that something similar to this is used by snipers, or more generally in artillery. They use objects available (hands, pens, cloth buttons, etc...) to determine the approximate distance to the target.