Well, without a profound knowledge of Christian writings and also the background of the ancient classics, I would say that just reading Seneca is not of much use for the Catholic.
His professed Stoicism is not exactly the best basis for Christian studies.
The reading and study of Classics has more to do with creating a educational basis for Catholicism, especially in regards to the Natural Law, and also to understand the Greco-Roman foundation of the Christian world.
I would rather recommend Cicero´s works on rhetorics and state philosophy as well as Aristotle.
But also these might not be useful without necessary foreknowledge and a strong spiritual life.