Start calling them and having conversations with several agencies. Who you might want to work for will only become clear then. Every agency has their fans so asking for popular opinion before you even know what you want may not be too useful.
Some suggestions: do not give them your phone number until you've talked to them several times and are serious. You might even protect yourself by dialing *67 before calling to block caller ID. Otherwise you will be wasting a lot of your time and theirs and getting lots of calls. Forever.
You will find that you will not be too marketable with only a year of experience. Some hospitals require two years of travel before they will consider you. The standard advice in this market is to have at least two years of staff experience, and then perhaps not be overly picky about your first couple of travel assignments. Then you will make a good go as a traveler!