First of all, study the Bible. A little bit a day, reading good, old, based study guides. "Study to shew thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth."

Then, start getting into the Church fathers and older academics. Aquinas, C. S. Lewis, Spurgeon, and some of the newer Orthodox writers (Josiah Trenham is a treat to listen to).