Get trained ,and documented, on everything you can. Take classes if you have time. Get meter time if the plant allows.
In short, pay attention. If you stay on it the opportunities will be there. Do a good job,your reputation will travel with you.
Don't obsess over tests,you should have 6 months to a year,more or less depending on how things go, before you start taking tests. Don't wait, only you know how much you need to study. A good start is here at nukeworker. Look at the material here as a guide to what you need to learn. The pay will vary.
Its difficult to maintain a relationship on the road. You can if you really want to but you have to be disciplined,if you know what I mean.