A silver coin is sometimes used to represent the full moon in divination, so why not carry it a step further and use the energy of the full moon to bless a coin to keep with you for good luck?
Gather these items:
In the light of the full moon, settle down before your cauldron and place the coin in the center of the cauldron. Fill the cauldron with water (about halfway is fine), and stir it clockwise seven times with the rosemary sprig, saying:
Luck be mine, luck come soon,
Let the coin rest overnight, then pour out the water carefully. Dry the coin and carry it with you in a special place.