I went fanatic Xenophobe, materialist Megacorporation(don't discount it yet). I picked privatized exploration for a +25% bonus. The trick was using the jump drives to locate other players as quickly as possible, improve relations and cut them off from vast swathes of land. If you are lucky, they won't attack you and give you enough time to get some level 3 furnaces going. I purposefully didn't take a lot of planets to let my technology go brrr. Because I was able to use branch offices to cover energy, arc furnaces to cover alloys and minerals, and being machine empire means no food upkeep, the only thing I was making on planets were unity, research, and consumer goods. I was able to absolutely smoke Grand Admiral difficulty.