Hi,
Screen shot from the schema for reference.

The Bare minimum is just the primary key, but that's not meaningful.
You need to ensure that you can populate as much information as you can so that reporting can work because you are not building tracking logs here, so you need to get, address, status, recipient Id, msg id and delivery id. after that you need to import tracking logs so that tracking reports can work. you will be building a workflow to import and create all these fields and relationships.
Regards,
Amit