The first question to ask is, "Do you need it?"
For true Agile practitioners, using the knowledge to develop great products that win in the market is the critical result to fight for. Agile certifications only help you to land a job. It gives you basic knowledge so you can get started. You will only complete the circle if you can practice it at work and keep improving your skills to help your organization improve.
If you decide to obtain a Scrum certification, 3 top-tier accreditation associations exist worldwide. They are Scrum Alliance, Scrum.org, and Scrum Inc.
Next, you need to decide which trainer should be your teacher. Please read "Are there different levels of Scrum Trainers in the Agile industry?" to learn more about the accreditation associations and steps to identify good trainers.