My sister, Nancy, made this pretty birdbath from an inexpensive ceramic saucer that goes under a pot.
Start with your base.
We adhered the tiles and glass baubles with an all-in-one grout (meaning we glued the tiles / baubles to the base piece and then used the same grout as the filler between the pieces). Grout comes in two basic types, and the choice of which one to use depends not on the tiles but on the width of the joints between them. Narrow joints of 1/8 inch or less call for unsanded grout. Joints wider than 1/8 inch get sanded grout. The sand helps bulk up the grout and keeps it from shrinking in the joints. You can add color to your grout (or buy it colored), I've even added acrylic paint to my grout. Once your tiles and baubles are in place, let dry, following instructions on the grout.
Smear grout over your tiles / baubles with a float. Let dry for a little bit (again, following grout instructions) and then get out the elbow grease and start wiping the grout to remove the excess, rinsing your sponge often.