A good thing to do early in your GDPR implementation is to create a Data Map for your company. This is a flow chart that identifies what happens to the personal data that enters your organisation. It should show where the data passes through and ultimately where it ends up.
Having created your flow chart it then positions you to determine which areas need to be prioritised to receive attention.
For this and further information on becoming GPDR compliant follow this link to Simply Shredding's YouTube Channel
Below is an example of what a flow chart could look like