Planets you might want to consider are any of the ones which have outfitters which only have about 4 items for sale - you know, missiles, laser cannons and auto-refueller. These are low-tech planets, and so have pathetic defense fleets. If you don't know which ones these are, look at what you can buy at Diphidia, and thengo look at other potential planets - they should be about the same. Diphidia only has a defense fleet of defenders, and so is easily taken. But i find it more fun to overrun the systems owned by the government you hate - the feds in my case. Its a good laugh, in the end.
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Given that God is infinite... and that the Universe is also infinite... would you like a muffin?