Freeorion cheats?

[MatGB]

The Super Tester building is hidden in the Release versions of the game, you need to be playing with a Test release to access it easily.

To give yourself advantages in game, you can start by editing the existing files, it's better to not add new things initially, but you can improve existing stuff relatively easily by simply changing numbers in whatever file you want to change.

For example, you can change your starting species to make it more powerful, then only an AI with that species gets the bonuses, but it won't know it's got them for the most part. Great/Ultimate Weapons and Attack Troops are obvious starts.