For optimal job flow concerning data import from a PIM system, the sequence should begin with downloading files globally from an SFTP site, followed by importing data into the B2C Commerce platform:

First flow: Download files, ensuring all required files are available and ready for import.

Second flow: Import the storefront catalog which likely has dependencies on the master catalog but is generally smaller and can be updated more rapidly.

Third flow: Import the master catalog, as it typically contains the foundational data needed for various site functionalities.

This sequence respects data dependency and integrity, ensuring that the storefront reflects the most current and accurate information after all relevant data is imported.