In the early 2000's I was obsessed with making things out of items you can buy in bulk. I found a novelty company that sold bouncy balls and another one that sold small industrial magnets.
The best adhesive I found was Uhu Craft Glue. I used cookie sheets and laid out the magnets like cookies. I would glue 4 dozen magnets a day. It took a couple weeks. I started with the front of the fridge and learned something important. People like to touch stuff. When stuff looks tactile, people want to and will rub against it. There were always several superballs bouncing around the kitchen.
The side of the fridge is also magnets, but it's glass beads with individual images. They were easier to wipe down.
BONUS: about 6 months after the superballs were installed, I happened to be up late one night and walked into the kitchen to discover that 75% of them glow in the dark.