Jewelry are items that you can buy at the Shop to instantly boost Refinement — even beyond its limit — and Love. The jewelry for sale changes randomly (necklaces, rings, etc.) The first five each increase Refinement by a 1/60th their price and Love by 1.
After you buy a jewelry, your slave will thank you. After the fifth, she also says that she has enough jewelry for any occasion, then any more jewelry that you buy will only increase Refinement by 1 and Love by 0.5 regardless of what its description says. Depending on the slave's Refinement limit, this may be the only way to max it.
In order to attend the High-Class Party, you need at least 25 points of Charisma and/or Refinement from items. Buying many pieces of jewelry is the only method of achieving this guaranteed to be available to all slaves; however, the Nymph's Tiara can also help, and most slaves have useful dresses as well.