If you would like to go deeper in your study of this letter, I highly recommend Christ-Centered Exposition: Exalting Jesus in Ephesians written by Tony Merida. Another study tool I recommend is buying a study Bible if you do not already have one. I highly recommend the Reformation Study Bible available in the English Standard Version or New King James Version. I also recommend the ESV Study Bible. For students, I recommend the ESV Student Study Bible. 

To explore the idea of spiritual warfare, particularly the armor of God, I recommend The Whole Armor of God written by Ian M. Duguid published by Crossway.