Traditionally the base tea is usually a strong black tea such as Assam, so that the spices and sweeteners do not overpower it. Usually, a specific type of Assam is used called “mamri”. Mamri tea is tea that has been cured in a special way that creates granules as opposed to “leaf” tea. It is inexpensive and the tea most often used in India. However, a wide variety of teas are used to make chai. I recommend using a black tea that suits your palette, but just know that most chai tea recipes typically use a strong variant of tea.