glitter glue (I purchased mine from walmart)
borax mixture (1tsp of borax mixed with 1 cup of water)
You want the glitter slime to be able to be very thin when stretch. You can store the glitter slime in air tight containers. If it becomes too dry or too wet you can always add water or borax solution (save the left over that you made).
You can see a video of how I made glitter slime below: