In the Space Stage, there is no way to "win" the game. It simply does not end, even if you have destroyed the Grox, collected all the artifacts, or have become a multi-millionaire. Once that all happens, you are probably down right bored with that saved game file. One thing to do with your god-like empire is to conquer the galaxy.
- Create a save starting from Cell Stage. The bonuses you get from Consequences are very important. For Cell Stage, Carnivore is the best option for the additional firepower. For Creature Stage, the Adaptable bonus speed saves a lot of time, Predator 1.5x HP is tempting, but in the long run you won't need much HP after defeating the Grox. None of the Tribal Stage bonuses are particularly important but the discount on the colony tools saves a few trips. The resulting archetype doesn't matter since you can change it later (except to Knight).
- Play the Space Stage normally until you can purchase monoliths. Terraform every purple and pink spice planet near your homeworld to T3 and put a monolith on it. If you're not a Zealot yet, switch to Zealot and use the Fanatical Frenzy superpower to capture the resulting empires you uplifted. This will provide you with easy money whenever you need it.
- Destroy all your neighbors. The way the game works: empires start with one planet and develop as long as you are nearby. Therefore the strongest empires in the galaxy are you, the Grox and your neighbors (assuming you have one save).
- You might want to ally with the Grox to get the Dance With The Devil badge before destroying them, but this is optional.
- Destroy the Grox. There are several methods to do that.
Conquering Itself Edit
With the Grox out of the way, the rest of the process is repetitive and time consuming. Capturing every star involves placing a colony on one of the planets. It's preferable to place one on a T1 plant-only planet. If those aren't present, T0 is preferable. This will prevent eco-disasters. Other empires are easy to deal with: simply use the Fanatical Frenzy on their homeworld. If they happen to have more than one planet, always deal with the homeworld first. T0 colonies are impossible to capture unless it's their homeworld so it saves you a Colony Incredi-Pak. If Fanatical Frenzy is on cooldown, simply save, exit to main menu, and reload the game; this will reset it and end the cooldown. If that strikes you as cheating, simply de-terraform the planet back to T0 and all the cities will be taken care of in one mega bomb shot.
Other empires are one of the smallest of your concerns; the biggest time wasters are systems that contain a Tribal Stage or Civilization Stage species. In order to place colony in such a system, you have to destroy every single tribe/city. The easiest way to do this is to de-terraform it to T0, which will instantly destroy the species and enable you to place a colony. The Scientist weapon, Gravitation Wave, may also be used but, due to the large reload time, it's unreliable. Reloading the game is slower than de-terraforming.
Despite popular belief, pirate attacks and Eco Disasters don't increase in number with the size of your empire. Pirates are harmless and can easily be ignored. Eco Disasters can be manipulated to happen close to the part you are focusing on capturing: the game will try to cause an Eco Disaster on a planet without a Bio Protector and Bio Stabilizer, meaning you just have to place one of each on every non-T0 planet except for one which is close to the zone you are about to conquer. This will make you able to respond very fast, therefore you don't have the risk of having to travel half the Galaxy.
- It is very difficult and nearly impossible to complete this goal. The sheer size of the galaxy means it would take a lot of patience and commitment to conquer it. The galaxy in Spore is home to several thousand stars, and most have planets suitable for colonization, by the use of mods or cheats you can make the task of colonizing large portions of the galaxy with relative ease.