What a clever way to use old invaluable glassware. Thrift stores are full of it. They often dump it by the trash can full. Before using glassware I plead with you to make sure the glass has no value. But if it does not there are endless ways to make these. Use epoxy to attach the bowl to the vase. If they are too heavy you may need to bury the base a little bit into the soil to help them stand up. If they break they are easy and cheap to replace. The designs are endless. I imagine someone handy could figure out a way to light these up. Maybe pain with a clear glow in the dark paint? Can you imaging a garden with a bunch of these throughout at night time all lit up.
We all know all the cool project you can make with Terra cotta pots and saucers. These are cool and very easy to make. Use any combination of sizes to make a non-unified look. Paint with your own style using acrylic pain. It will soak a bit into the saucer/pot so a second coat might be needed. You can certainly just set them on top of each other or glue them together with liquid nails or E6000. Carry this project further by adding little miniature figures of elves and fairies on top and make it look like this is their own secret world. This project is cheap and using existing items you already have increases your savings.