Spend it on your politics like Soros or Koch. Accelerate technical progress like Musk. Pure vanity like that guy who spent $600m getting the Chicago GSB named after him. I’m sure if you tried you could come up with some ways you’d like the world to be different that you could spend a lot of money on. Personally I’d love to see well recognized, respected tests that test the same knowledge as a variety of university degrees. Setting up an organization to do that and giving prizes for the top results to build brand awareness for the first decade could easily burn a million dollars a year for a decade for one subject. Advertising is expensive, organizations are expensive, people are expensive, especially qualified, competent ones.