Great idea for a gift or just stuck in the house needing a rainy day activity...also won't cost you an arm and a leg to do.
What you need just depends on what you find, my daughter was lucky to get for Christmas a "Painting Glass Stones" kit from her Aunt and Uncle. The funny thing is they didn't know I had already planned on doing this project with Riley myself.
If you aren't lucky enough to find a kit this is what you need: paint, brushes, strong clear drying glue (I went with Gorilla), magnets, and glass beads. Glass beads/stones should be relatively easy to find. I found ours at the Dollar Store, but I know almost all craft stores carry them. I also used a cheap plastic table cloth, just in case any glue escaped me, but can also come in handy for the painting step. One thing not in pictured that I wish I did was get white card-stock! That step that I wish I did will also require a pair of scissors.
My daughter and sister actually had a fun day and did the painting step while I was having a sick day, but as you see from above they turned out cute. Just paint the flat (underside) of the stone/bead, remember the image is kind of working opposite, mirror like. Let it dry. Acrylic paint doesn't take to long to dry, but if you want to be safe wait a day, paint side up while drying.
Now that it's all dry, squeeze a TINY bit of your strong glue. I devoted a cheap paint brush to smearing it around. Now, if I had thought this out I would had placed a piece of white card-stock to that so the magnet wouldn't had shown through so much, making the paint a little hard to see sometimes. Probably a little square piece and cut it out exact once that step had dried, then repeating with more glue and a little smear. Another idea is tracing the stones and cutting the paper out, I guess it's just up to you.
So let's pretend that painted backside is now a white card-stock part with strong clear glue, drop the magnet to the center. Press it on hard. Let dry. If your glue is like mine it won't take long at all.
All done! Ready to work their magnetic magic on your fridge. You can see in the close up why I wish I added the white paper step. Oh well, there's always next time.