If you're looking for a rich and creamy gravy for classic dishes such as Southern-style biscuits with white gravy, you won't get it from a gravy made with almond milk instead of whole milk and heavy cream. But if you want a white gravy with fewer calories, if you're allergic to dairy milk and need an alternative or if you use almond milk gravy with flavorful roast beef or well-seasoned chicken and dumplings, then almond milk will work well enough.
No Need for Recipe Changes
Almond milk and dairy milk are interchangeable when you substitute one for another in any recipe. The typical proportions of 3 tablespoons of flour to 2 cups of milk for a gravy with medium thickness work with all types of milk. For thicker almond milk gravy, as for thicker dairy milk gravy, increase the amount of flour you use. For thinner gravy, use less flour.
Add a Little Fat
Because almond milk has less fat than cow's milk, it lacks the richness that milk gives to gravy. To compensate for this lack, and if calories aren't a concern, use butter instead margarine to make your gravy. Or, add some cheese to the gravy for extra flavor and richness. Parmesan cheese works well with most recipes that call for white gravy and adds both depth of flavor and richness to the gravy.