Well, let me tell you some more. All the systems I found so far are in one straight line connected. (hope none of you are ancient race else you'll know where I am).
I colonised all there was in my home system and the next one. Then I get 2 empty systems, then a juicy one with 3 more breathable planets. So I'm constructing a deep-space colonisation fleet to go grab that system. Problems: it will take me 6 turns to get there. And I can't afford the maintenance on the fleet, all my planets are crap for minerals. Plus there's 2 more wormholes (unexplored) leading to the juicy system...so I hope none of you beats me to it. Just in case I am delaying my fleet send-off one turn so I can arm them to their teeth