Expand Your Borders
If a player drops or is crushed, claim the planets closest to the next opponent, first. While you want SOME planets in between as supply lines, you want to stake your claim on planets as far out as possible, thus extending your own border. The diplomatic implications of someone attacking planets you already have clans on is different from claiming planets that you INTEND to develop, but haven’t done so. In the latter case, an opponent can call your bluff on where you borders actually lie, but if you have clans present, your claim can be substantiated. Most opponents will not explore much deeper into “your” space than the border planets, because he won’t have supply lines through that area, either.