For recommending a scattershot of Church History, I've developed the ABCV model: read Augustine, Bonaventure, Calvin, and Vos. With those you'll have a good sampling of four people the four eras of current Church History.
The biggest gap in most everyone's Church History knowledge is by far and way that which is colloquially known as the medieval period (~500-1500). There's of course no such thing as the medieval period, the concept itself is a product of some enlightenment folk trying to mock a period of history they didn't like. The reformers would sometimes engage in this mockery too, often stretching and shrinking the time frame for the medieval world as it fit their agenda. For example, when Luther likes Bonaventure, he's not a medieval theologian.
For the medieval era, in the ABCV model, Bonaventure gives you a good idea of his era, but when you read later authors, you can see how he connects to the reformation. Calling Wyclif and Hus the forerunners of the Reformation is a bit odd, since there are many others who did a better job of doing that job. Bonaventure is on that better list.
There is a cure for ignorance of this period: a lot of lectures and reading.
Medieval Church (Clair Davis, 1980, WTS)
This is the top lecture series you want to use to guide your study. His focus is history, not just historical theology. As odd as this may sound, that actually makes him unique. * WTS
Medieval Church (Carl Truman, 2002, WTS)
You never want to have a single resource for the study of any historical topic. His focus is further toward the historical theology side of the spectrum. * WTS
The Harvest of Medieval Theology: Gabriel Biel and Late Medieval Nominalism (Heiko Oberman)
While some professors take issue with Oberman's rose-colored perspective of the medieval period, I find this work to be incredibly helpful in getting a grasp of the theological connection between the late medieval period and the reformation. This work specifically zooms into the theology of Gabriel Biel, a figure you must have familiarity with in order to understand Luther. If you've never heard the name Gabriel Biel, your entire understanding of Luther has been filtered through a hagiographic lense.
You should read this book with Alister McGrath's Iustitia Dei. This work tries to correct some of the harsher accusations of heresy that Oberman lays against Gabriel Biel.
The Dawn of the Reformation: Essays in Late Medieval and Early Reformation Thought (Heiko Oberman)
There are some authors whose entire corpus is required reading for a particular period. For the late medieval period, Heiko Oberman is the one. The chapters in this book can largely be read in any order.
Great Medieval Thinkers
In addition to the lectures, you'll want to dive into a few major figures in Church History. The Great Medieval Thinkers series is excellent for this. The following are some that I've worked through and found quite helpful: