I would not recommend that you go into travel nursing directly after graduation. To be successful at travel nursing, you need to have very solid clinical skills, and that's something that you develop over time...it doesn't happen just because you've graduated. Travel nurses have to be very flexible and need little direction. Think about it...you'll be switching from one hospital/clinical setting to another. The hospitals you'll be going to will expect you to be able to function independently. As a new grad, that will be difficult.
I would suggest that you give yourself a year in one hospital after you graduate to sharpen your clinical and time management skills. It will make you a more attractive candidate for the position you're looking for, and will give you a foundation to draw from in future jobs.
As far as certifications, it depends on which organization is offering the certification. Usually they require a minimum of 2y experience, and there's a certification exam (obviously). The ANCC offers certs. in many areas, but a lot of specialties have their own professional organization that offers certification. My personal opinion is that being certified by the organization that represents the specialty is better than the certs. offered by ANCC (part of the ANA). For example, my specialty is hospice/palliative care, and the HPNA (Hospice and Palliative Nurses' Assn.) offers a certification, but so does the ANA/ANCC.
Hope this helped a little.