What to do after ITIL Foundation Certification?

Generally speaking, your road in certification is defined by your current
role and career path. So, if you are a IT professional serving in any of the
ITSM areas; change manager, capacity planner, service desk manager, etc, then
most likely your next step would be to get a ITIL® Practitioner certification in
your field of work. However, if you are an IT manager; for example, then you
need to skip the Practitioner and move ahead to the ITIL® Manager certification.
That’s the broader certification which will require knowledge of all ITSM

How does PMP fit in? Well, it depends on where you are standing.
If your role (or to-be) involves the responsibilities of managing projects, then
the PMP would be a good choice. The PMP touches on the
project management part of IT, and ITIL® touches on the operations

If you are up to implementing a CSIP (Continuous Service
Improvement Program) for your organization, then you need to asssess your
knowledge in both areas; PMP and ITIL®, and make sure you leverage that to a
satisfactory level before starting the effort since you will need both knowledge
domains to bring the CSIP to a success.