USB C to Lightning Cable
When it comes to connecting your iPhone to your MacBook Pro, the best option is to buy a USB C to Lightning cable instead of using an adapter that is more likely to get lost or left at home. Sure, an adapter would double as a USB adapter for other devices, but we're looking to remove adapters as possible.
Apple sells two official USB C to Lightning cables, and you can also buy a well reviewed third-party option for $7.
USB-C to Lightning Cable 1 M - $25 at Apple
USB-C to Lightning Cable 2 M - $35 at Apple
USB-C to Lightning Cable 1 M - $7 at Amazon
You can use this to charge your iPhone or iPad, sync to iTunes and even to use with Duet to use your iPad as a second display for your 2016 MacBook Pro.