What is the best method for operating U.S. 115v Lights On 220v European Supply

Use European 220v light bulbs?

Step down transformer?

European bulbs have a different base than ones in the US. (I once re-wired a fixture a woman bought in England)

You can buy 240 volt US medium base bulbs at an electrical supply house, or else remove the American light sockets, install European style sockets and use standard European light bulbs.