So this will depend on what story you want to tell on your wall. I’m happy to give you some examples from my personal home.
Our staircase gallery wall is meant to tell the story of our family over the years, so it includes wedding photos, newborn photos of my boys and I plan to update it with family photos we had done recently. These are all from professional photography sessions.
Our living room gallery is meant to showcase our sailing adventures, it is mostly made up of iphone photos that have been edited and we swap it out every year so it is fresh.
A past client wanted to showcase their travel photos, so their wall is full of photos of them in other countries so they can remember their adventures.