Mostly equipment for the day I might venture out on my own.
I have an entire music studio (hardware and software), creative studio (cintiq, nice cameras [video and still], adobe creative suite), and the start of an electrical engineering lab in my apartment. I have built a pretty good home theater in my living room (projection system), and lots of DVDs for inspiration. Lots and lots of boooooks.
It's pretty expensive, but makes me feel more secure. I'm not worried about money; I am worried about boredom. Make sure to get good insurance.
I would spend some of it curating a taste in something as well.
The most important thing you have to spend is time. Whatever you can buy to save time (without losing control over things you need control over) is a good investment.