Go to Settings -> Privacy, and slide many (most?) things to off. Including Diagnostic & Usage Data to Basic.
Settings > Personalization > Start and slide "Occasionally show suggestions in start" to off.
Settings -> Personalization -> Lock Screen and slide "Get fun facts, tips, and more from Windows and Cortana on your lock screen" to off.
Settings -> System -> Notifications & actions -> "Get tip, tricks, and suggestions as you use Windows" and "Show me the Windows welcome experience after updates and occasionally when I sign in to highlight what's new and suggested" to off.
Go to Cortana (Taskbar) -> Settings (Gear Icon) -> "Taskbar tidbits" to off
I wouldn't use the built in "Mail" app with or without ads, it is terrible. Just have him simply not use it.
Edit: Sorry. It's now a paid software. Checking for free alternatives. Found one: shutup10
Lastly, install Unchecky. It'll automatically uncheck options for additional unwanted programs, adware, toolbars... when installing software.
If you stay within the Settings UI then you are working within Windows 10's supported design. When you run a script that disables a system service (e.g. Cortana) things start to get quirky/broken.
Several of those break Windows Update for example.
Some people might consider that a feature /s.
https://community.spiceworks.com/scripts/show/4378-windows-1...