The agencies all require a year of experience. Many hospitals want 2-3 years, especially in critical care areas.
Think about it- as a new grad in a staff job, you're going to get weeks of orientation and supervision. It costs a lot of money to hire and orient a nurse. When you're a traveller, you are expected to pull your own weight day 1 or 2 at the latest. They don't teach you how to be a nurse, just how to do their paperwork. You need and deserve a proper orientation. Nursing school
teaches you very little about actual nursing.
Lots of new grads want to go right into travelling. But you need to be properly oriented and able to function on your own. Hospitals pay a lot of money for travellers- you're there to solve problems for them, not to be trained.
There are a couple agencies that will hire with 9 months of experience. Whether that is enough or not is something you will have to see for yourself. There are a couple agencies that offer "internship" contracts but I've never heard anything good about them. They are for long periods of time, pay less than regular contracts, and if you want to quit it costs you a bundle. Since you'd be in one place for a while anyway, it's better (IMHO) to take a staff job, get the benefits that travellers don't have, and get properly trained.
Good luck. See you on the road in a year or two. <g>