A solar system. A minor one would do. Nothing too big. I wouldn't want to appear ostentatious
It would have to be local, because I don't want to put up with excessive travel time. A galaxy would be too large, and far too time-consuming to travel around in. And a galaxy cluster would be impossible So a solar system would be just about right.
The reason for a solar system instead of just a planet is the question of spares. With multiple planets, you can play around a bit first. I could drop a few asteroids onto planets, or maybe smash a couple gas giants together to make a proto-star. Way more choices, and free do-overs!