As in: what did they want to achieve with their breeding programs and "learning how to learn"? Assuming that the Kwisatz Haderach was as they intended, what was next?
Rebecca and the Rabbi discuss the ultimate goal, the "grail", of the Bene Gesserit in Heretics of Dune.
"That is wisdom. What is it the lady says they seek?"
"Influence on the maturing of humankind."
[...] Perhaps they have been too long on the road to Damascus without a blinding flash of illumination, Rebecca. I hear them say they act for the benefit of humankind. Somehow, I cannot see this in them, nor do I believe the Tyrant saw it."
When Rebecca started to reply, he stopped her with an upraised hand. "Mature humanity? That is their grail? Is it not the mature fruit that is plucked and eaten?"
Odrade says something similar in Chapterhouse Dune:
Survival of humankind took precedence over survival of the Sisterhood. Else our grail of human maturity is meaningless.
The Bene Gesserit say and truly believe they "exist only to serve." To them, that means guiding humanity to "maturation." The Bene Gesserit do not seek direct power or control over the affairs of mankind except insofar as it is necessary to achieve their long term goals - they believe that would only make them a target and lead to their destruction.
Their plan was total political and religious power:
As the Bene Gesserit taught for centuries, long before they ran afoul of the Freman:
"When religion and politics ride in the same cart, when that cart is driven by a holy man (baraka), nothing can stand in their path."
- Appendix II: The Religion of Dune