Well, using your estimations there, if we could get to mars in 30 minutes, we'd be traveling ~100 million km/h (which is about average distance from earth at 200 million km, if you timed it right it could be only 56 million km away or if you timed it bad, on opposite sides of the sun). That is about 1/10th the speed of light (at 300,000 km per second, or about 1 billion km per hour). The planets we could reach within a single generation would be very small and taken over fast (We could get to the next closest star in about 40 years, which I don't actually think has any planets within it's habitable zone).
Sorry, to the point of the topic. I would probably take over a planet that had very limited access from anyone, just because I like being alone. I'd probably call it "Don't Come Here" with like a middle finger as the flag in hopes to keep people away. I'd probably spend all my time playing video games and cooking new exotic foods.