Here are all the planets in the universe. If you want to conquer a planet, you have to defeat everyone on the planet. If there is no one, then it looks like you made out. When being challenged for a planet, you cannot decline. When you take over a planet, you can put a tool booth of up to $50,000 that people have to pay to get on your planet.
Earth-This is where you start out.
Namek-Takes 10 hours to get to from Earth.
Kinassa-Takes 1 day to get to from Namek.
Planet Frieza-Takes 3 days to get to from Kinassa.
Dark Star-Takes 5 days to get to from Planet Frieza.
Saiyan Elite Base-Takes 1 week to get to from Dark Star.