You might better off on a smaller map, where you can at least rush one of the Unfairs and take it out of the game early. The AI's, even the Unfair ones, are vulnerable to early LRM rushes, since they tend to love to stick with light frigates that LRMs chew to little tiny pieces.

On big maps where you start flirting with the fleet capacity, unless you're Vasari with Phase Gates and can be literally anywhere in one jump, you'll have real problems making large offenses capable of defeating an enemy fleet while still protecting your own worlds.

I would recommend either going for Vasari for the Phase Gates and their larger fleets, or Advent and concentrate on getting multiple level 6 and higher capitals, since a relatively small Advent fleet built around a Progenitor Mothership with level 3 Malice and a Radiance Battleship with Cleansing Brilliance With Guardians, Illuminators and a few Subjugators (optional) can defeat incredibly large fleets of the AI since it loves bunching up it's units and begs for a good Brilliance hit.