Reddit mentions of Documents Early Christian Thought

Be careful about what you bought, it's solid stuff, but those translations are from the 19th century and may not be very clear.

If you want something manageable like an anthology, I would recommend these. They're organized by topic so it's easy to look up stuff you're particularly interested in.

• Documents in Early Christian Thought, ed. Maurice Wiles and Mark Santer
  
  Miles was a renowned patristics scholar at Oxford. He also has a good introduction to the Church Fathers here. Another good intro to the Church Fathers is Boniface Ramsey's Beginning to Read the Fathers. (It was revised recently but for the sake of cost, IDK how necessary it is to get the newest edition.)
  
  
• The Early Christian Fathers, ed. Henry Bettenson
  
  From the Apostolic Age to Athanasius.
  
  
• The Later Christian Fathers, ed. Henry Bettenson
  
  Post-Nicene stuff. It stops at Chalcedon with Leo the Great's tome.
  
  
• This series from Fortress Press is good: Sources of Early Christian Thought. Its a series of anthologies organized by topic. So instead of one-volume anthologies with multiple topics, it's one anthology for the Trinity, Christology, etc. which allows for something more in depth.
  
  
• Finally, St. Vladimir's Seminary Press publishes a Popular Patristics Series. It features an edition of Athanasius' On the Incarnation with an introduction by CS Lewis himself!
  
  As to really important figures (I'm just listing what comes to mind):
  
  
• Origen
  
  
• Irenaeus
  
  
• Athanasius
  
  
• Augustine
  
  
• The "Cappadocian Fathers" (Gregory Nazianzus, Gregory of Nyssa, and Basil the Great)
  
  
• John Chrysostom. In Orhodoxy, Chrysostom is often grouped with Gregory Naziansus and Basil the Great as the "Three Holy Heirarchs", as the tradition's seminal bishops.
  
  
• Similar to the Three Holy Hierarchs, Catholicism recognizes the "Four Latin Doctors" for their influence: Augustine, Ambrose, Jerome, and Gregory the Great.