The first hurdle has been cleared. Always
the most-important one, and please be assured that my accolades are quite sincere.
Now ... you have a lot
of work to do. A lot of planning
Once your (justifiable...) exuberance at having landed your first job begins to settle down ... and don't be in a hurry for it to settle down, because you do quite-richly deserve it ... I want you to start thinking about it from your (new) employer's business
What does this company need from the person in this position? What does the company's business need
for the person in (your) position to "bring to the table?"
Never mind(!) what insecurities you may have, or what sort of "validation" you may have been seeking .. from certifications or diplomas or from what-have-you .. you're "in" now.
What does your new employer's business need?
Presumably the person who gave you the thumbs-up knew more-or-less what (s)he was hiring, and will be well-satisfied with that decision. No matter how nervous you may (quite justifiably) feel... no matter how inadequate the gremlins in your "anxiety closet" might be trying to make you feel ...
Put on-hold any plans
for "more certifications" and focus on the (new) job
at hand. Plant a large boot squarely in the face of any insecurities and try your best to anticipate what your new employer needs the most
from a person in your position, and perhaps what your employer hoped in their wildest dreams to find
in that person.
Try to be, or in due time to become, that