As an Ancient Race, I can see all the map. I pick the 39 most strategic locations on the map before I start a game. Generally they are 3-4 warp points apart so that any planet in any system is within range 50 of colonizing by my seed colonies. I build up the facilities and population on my seed colonies, then blitz attack/ expand about turn 120 when I have all the critical ship tech. The limit on seed colonies is about 40-45, after that the AI complain about your planting too many planets and go to war, losing trade treaties. This is not the Mega Evil Empire limit, that comes later.

If you are not an Ancient race, I do not know what to suggest. BE ONE.