I have seen bottlecap magnet sets in lots of high end gift shops selling for $8-15! For about that much you can really easily make a whole bunch of them! And it's really fun too - you get to play with chemicals :)
I chose to use a two-part jewelry resin to fill in my embellished bottle caps. Yes, I've seen other people make similar projects using Crystal Effects, but the jewelry resin is specifically designed for this type of use, and I feel that it will hold up and stay looking nice in the long run.
I decided to go with the More Amore DSP for a Valentine's Day look, but you can certainly use whatever DSP you like. You can probably use a stamped image too - I haven't tried it but I bet it would work fine. Just make sure your ink is completely dry so it doesn't run when you add the glue and the resin.
I've got a video on this project for you too. Just one important note - If you want to try this project, make sure you follow the directions for the resin that you purchase. It will probably be similar to what I do, but may not be exactly the same. The video is below, or remember you can always watch it over on my YouTube channel. If you have any questions, please let me know!
Happy Stampin'! :)
Soda Pop Top Magnets Supplies