There are two 'easy' and older ETS practice exams and two 'hard' and more recent ETS practice exams. If you are going to take each of the practice exams once, I would recommend this:
Take one of the hard exams first. These are the closest to what you will actually encounter on test day. If you start off taking the easy ones you might get lulled into a false sense of security. After the first practice test, you can plan which materials you need to study more intensely. I would also recommend taking the other hard one last. As for the order of the Princeton exam and the other two ETS exams I don't think it matters that much.