This is the recipe I’ve used with success:
Silver or gold for piping
2 teaspoons gold or silver luster dust
2 teaspoons powdered sugar
clear alcohol (like vodka or ever-clear or you may use lemon extract, but very sparingly as it dries differently)
1 teaspoons of clear piping gel
Mix the luster dust with powdered sugar, then add a few drops of alcohol to form a paste. Add piping gel a little at a time till you get the correct consistency for piping. Store leftovers in an airtight container in the refrigerator. It will last indefinitely.