One of the most significant decisions you'll make early in the game is choosing which of the three houses to lead: the Black Eagles, Blue Lions, or Golden Deer. Each house has a distinct leader, unique students, and a different narrative path, influencing the story's progression and the characters you'll interact with most frequently. Your choice will also determine the initial set of units you have access to.
Consider the personalities of the house leaders and their students, as well as their starting proficiencies. The Black Eagles, led by Edelgard, often excel in magic. The Blue Lions, led by Dimitri, are strong in physical combat. The Golden Deer, led by Claude, offer a balanced approach with a focus on bows and strategy. There's no 'wrong' choice, but each offers a unique experience.