I agree with @GLOBAL_TEACHER. If you're set on heading overseas then the Tier 3 schools would be the best bet.
Another thing to consider is to start your teaching career in the States and then go abroad after two years. I'm sure this isn't universal for everyone, but in my experience my first two years teaching were the hardest. I couldn't imagine going through that learning process and having to juggle all the issues of being in a new country at the same time. There's a HUGE learning curve when you first begin teaching. Most school districts in the States have new teacher support programs and/or mentor programs that you wouldn't have access to at an international school. Those programs were really instrumental for me as I was getting my footing as a teacher. Again, I can't claim this is a universal truth across the board, but it's been my experience.
Those are my two cents. Let me know if you have any more questions and I wish you luck in whatever avenue you pursue!