Tips for Kubernetizing / containerizing a PHP app?

I want to upgrade an existing PHP7 application to run on Kubernetes / Docker, because of the scalability options. The application is an asset management system that mimics an OS-like folder structure (files stored in one upload path, folder structure is just database relations) and is able to upload (potentially huge) files (admins) and share these files (users).

I have never used Docker / Kubernetes in practice, but read a lot about it and understand the principles and uses of images, containers, services.

I realise this is a very global question with such little information, but could anyone point out some important things to take into account?