Q: How to reset my iPad to sell but not loose photos etc

Taking it back to Factory settings will delete everything from the iPad Air, but does not affect anything on icloud or other devices if that's what you are concerned about.

Follow the steps in this support document:

What to do before selling or giving away your iPhone, iPad, or iPod touch - Apple Support

Connect your iPad to computer and copy all the photos from the camera roll to the computer. Then factory reset and sell it.

Hello, welcome to Apple community. Reset your iPad will lose all data including your photos. I suggest you back up your photos at first. You can use a tool call iPhone Transfer. It's especially for iOS devices. You can back up photos from iPad to computer and then recover photos with simple clicks.

Hope this will help you.