I'm not sure what you mean by a "good fleet advancement system." Personally, I was looking for a group where everyone was pretty much equal. Check out UnrepentantGaming.com if that is of interest. If you want something different, then good luck to you.
Once you go 44th, you never go back... Just sayin...
Prime Minister Nayrok: Do not relax your security for an instant, Captain. He is extremely violent, and very cunning, as you already know. Jean-Luc Picard: A matter of internal security: the age-old cry of the oppressor. The Hunted [3.11]
As others have stated above, I'm not entirely sure what you're looking for in an advancement system.
In the Blacksheep, people with good attitudes will make their way up the ranks. Members who treat others with courtesy, are active in the game, participate and help others will likely be offered a seat on our Fleet Council given enough time. Also, a good sense of humor never hurts! Our advancement system is based on a person's attitude and how they treat others within the game.
Hope you find what you're looking for, and that you're enjoying the game!