Moving to a different country at 17?

Well, I'm seriously considering moving to Denmark.. Germany.. or England. All very beautiful countries right? I'm 17, and have been on my own since I was 16, and I mean compltely on my own, I have no family in the state I'm currently living in, and it doesn't seem to bother me really. and I've moved to 4 different states in the last yr nd a half. All by myself. yes I know, I'm probably not entirely ready for this but I don't feel I fit in, in America. Anyways, I was looking up how to become a citizen of each of those countries, and what I found was basically go there and don't come back, get married, or get a working visa with the possibility of citizenship being offered to me in the end. I don't want to wait till I'm like 27 to move to a different country because I feel by then I'll be old nd washed out, and it might be harder for me to make friends. Also I want to start school in the UK! I want to be a veterinarian.. I'm leaning more towards England only because I know so little German, and I don't believe I know any Dutch.. I've mostly lived in Cities growin up so I'm trying to stick to a well populated place.. with the perfect nightlife and underground clubs to keep me entertained. I also have a dog that I'll be bringing with me, are there alot of places that allow dogs in the home in those 3 countries? I know some places in the UK dogs are treated like Kings! Well.. what advice can you give me?