I gave up on a WC with Castille, because it was booooring.
I'll try a shorter timeframe - namely, I will try and unite Germany starting with the ascension of Friedrich the Great on May 10, 1668.
* Form Prussia (I start as Brandenburg, and can form Prussia as soon as I get 20 prestige)
* Connect the Prussian Lands
* Form Germany
* Become Holy Roman Emperor
* Take the Austrian provinces from Austria
* Humiliate France
* Make inroads into India
What will not happen:
* Taking land in America. The cost of doing anything in America outweighs the utility of anything I could gain there against major powers.
* Any aspirations to naval greatness. Again, cost issues.