You will want to make these shoes over the course of 2 or 3 days. The first day or two will be the preparation days where you get the shoe base ready for embellishment. The following day will be spent in a glue-gunning frenzy.
Day 1: Prepping the shoes
Make sure to cover your work area with plastic, tarps, etc.

Take your shoes and give them a gentle cleaning so they are dust and dirt free. Remove any price tags.

Using your sponge brush, liberally apply Mod Podge to one area of the shoe at a time.

Hold your Mod Podged shoe over your shirt box and liberally shake on one color of glitter. You will only want to work with one color at a time, letting that color dry before adding another color. Make sure that your glitter adheres to all of the Mod Podge. If need be, place your shoe on a piece of newspaper, and pour the glitter contents of the shirt box back into the glitter container. Repeat step 3 until the shoe is completely covered.

Set your shoe aside to dry.

When the shoe is dry, repeat step numbers 2 & 3 on different areas of the shoe. Keep repeating these steps until the entire shoe is covered in glitter. This is your base shoe. Let your base completely dry (may take 24 to 48 hours, depending on the weather).

Day Two: Embellishing the shoes
Using your glue gun, add whatever kind of crazy embellishments that you can gather.

At Mardi Gras, these shoes are worn like giant necklaces. If you wish, here's how to prep your shoes for a necklace attachment! Be sure to do this BEFORE decorating your shoe.
If you've got strappy shoes, simply tie a 3-foot length of ribbon from the ankle strap. For solid-backed shoes we use screw eyes/eye bolts. With a Phillips head screwdriver (or an electric drill -- but this requires an adult to do!), push a starter hole into the solid back of the shoe.

Holding the eye bolt with a pair of pliers, screw the bolt into place. Run a ribbon through the eye bolt to make into a necklace.