I would buy an island, 20mil gets you a nice small one so around 100mil should get you a good size one, then I would make it entirely self sufficient, with everything I could possibly need including a massive typhoon proof luxury bunker and some kind of floating dock about fifty miles away for weekly deliveries..
It would have to be at least five miles across so I could build a road course, drag strip and a banked oval.........
My fridge and pantry would be my own private grocery store(not huge) .....
There would be huge speakers (maybe on poles that look like palm trees) everywhere and the music would be cranked to concert volume.......
There would definetly be a cerain HOTTIE who would be welcome whenever she likes and to come and go as she pleases(using the batcave method of transport)
There would be massive partys (using same transport method as the HOTTIE)
And of course the house would have every conceivable luxury........
That covers most of the big stuff, I think a billion should cover it