You can find these at your local craft or hardware store. Glass or plastic fishbowls can be used as well.  You might consider plastic as a cheaper and safer alternative, especially if there are small children around. These tend to be smaller than the glass globes used for arts and crafts or lighting fixtures. Jars typically have spill proof lids, which is perfect if you are a mobile fortune teller. Once you have done this, allow the glue to dry. You will not be adhering anything to the hot glue, but will instead be using it as a seal. The dried glue will help hold the glass globe in place once it is seated on the cup. Stretch the cotton out as much as you can before stuffing it into globe. Try to avoid dense clumps, or these will block the LED lights you will insert.  The lights reflecting off of the cotton will create a mysterious glow. Use dye to color your spider web cotton and give the effect of different colored smoke inside your crystal ball. Clear vinyl and plastic might catch the light in a new and interesting way. Oven bags, tinsel, and streamers are also options. Try using two or more materials at once for more dramatic effect. You can find these at many stores in the home and garden section. LED tea lights come in a wide variety of shapes, sizes, models and colors. Some LED tea lights change color and can be controlled by a remote. LED tea lights are usually inexpensive. A quick Internet search should help you find what kind of tea light will work best for your crystal ball. The diameter of the glass cup needs to be larger than the opening of your glass globe so the globe does not rest flat on the table. A clear shallow bowl can be used in place of a cup. This is the first of two lights that you will be attaching to a clear drinking glass. The clear drinking glass will create the glowing base for your crystal ball. Gently apply a bit of pressure so you’re sure the glue adheres and allow it a few minutes to dry.  The LED tea light should now be glued to the bottom of the inside of the clear drinking glass. Most LED tea lights are activated by twisting the top into the bottom.  Be careful to only apply hot glue to the very bottom of the tea light so that you can still twist it on and off. If you are using a globe-shaped canning jar for your crystal ball, glue the LED tea light to the inside of the lid. You will glue this to the outside of the bottom of your clear drinking glass. You do not need to do this if you are using a canning jar.  You will not be gluing any more lights to the lid. Already having applied glue to the light itself, all you need to do is use a small amount of pressure to make sure the glue sticks.  The tea-light on the inside should be hanging upside down, while the tea light on the outside will remain right side up. Before mounting the globe onto the base, make sure the LED lights are on and working properly.  You will need to remove the globe each time you want to turn on or turn off the lights inside your crystal ball. Insert the drinking glass and its attached LEDs into the opening of the glass globe until it comes to rest against the dried glue bead.  The opening of the drinking glass will now be the base of your crystal ball, which should be glowing from the LED tea lights inside.  If your drinking glass is too small, it will slip all the way into your globe and spoil the effect of a raised, glowing crystal ball. If you are using a canning jar simply screw the lid into place. The LED tea light will now be hanging on the inside of the jar, surrounded spiderweb cotton. This will add to the over-all aesthetic of the crystal ball, and more importantly, conceal the fact that it is a globe resting on an overturned, clear drinking glass.  Black and red are classic fortune teller colors, and satin or velvet can give your crystal ball an air of elegance. If you are using the crystal ball as a Halloween prop, try matching the decorative fabric to your costume.

Summary:
Purchase a glass globe or a spherical lighting fixture. Peruse globe shaped canning jars. Run a bead of hot glue around the opening lip of the globe. Fill the glass globe with Halloween spider web cotton. Experiment with different types of filler. Buy LED tea lights. Find a suitable clear drinking glass to use as a mount. Apply a small amount of hot glue to the bottom of a LED tea light. Drop the LED tea light into the drinking glass so that it sits flush on the bottom. Do not apply glue to the ON/OFF switch. Apply a small amount of hot glue to the bottom of another LED tea light. Flip the drinking glass over and mount the LED. Turn on the LED tea lights. Slide the crystal ball onto the glass. Wrap the decorative fabric around the base.