Turn off in app purchases

Dear420 wrote:

I cannot figure out how to turn the in at purchases off on my phone so I can download apps without having a card on file (bold mine)

Anyway it wouldn't matter- Apple can require a valid payment method (which cannot be a gift card) for verification purposes. Turning off in-app purchases wouldn't change that.

Add a payment method to your Apple ID - Apple Support

You cannot turn off in-app purchases. It is the developer of the app that includes the in-app purchases with their apps. They put them there for a reason.