We all know that an iPhone or iPad or iPod touch is pretty limited in functionality without an iCloud account. Perhaps in your situation, Family Sharing would be overkill, or you have a need to keep this device separate from your regular iCloud account (troubleshooting, for example). Maybe you have a previous iPhone or iPod touch in use by another family member who doesn't have an email address. There's an easy way to set it up that makes it easy to monitoring all those receipts and the activity on that device.
If you want to filter friend requests or iCloud messages, here's an example.
When you set up the device, make sure it's using a sub-address of your main email. This is even more convenient if you set it up on the same address used for your own Apple ID. Now all the iTunes receipts and subscription notices and everything will come to your email address. With some rules or filtering for that address, you now get all the information from that account just like you do for your own.