Use jimmie sprinkles (the longer type) as they won’t bleed into your ice cream and other kinds will.
Use heavy cream (or half heavy cream, half Half and Half for a creamier ice cream base).
Add in up to 1.5 cups of mixins when you add the sprinkles. Some yummy options would be, chopped up Golden Oreos, or bite sized pieces of cake.
Use the powdered dry cake mix, not prepared cake mix.