There are many zones in the Expanse that are sparsely occupied (as of 19 January 2013)
If you are in a heavily populated zone you can trade more easily, but you compete for planets and mining sites.
If you are in an otherwise unoccupied zone, you have the resources of the whole zone to yourself and you can also be almost certain to win the lottery every day. The downside is that you might be attacked by AI who populate these remote regions when you come out of Isolation.
The following maps can be used to give you an idea which zones might make good colony sites.
Keywords: colony zone population