Usually practice basic movements such as sago, and the teacher needs to observe your leg movements in order to find and correct them in time. It is more convenient to wear pants, including the pace of belly dancing, and so on. You also want the teacher to wear pants, so that you can see the movements clearly and keep up with her rhythm. It is easier for teachers to teach in belly dancing pants than in skirts. It is convenient for students to understand the changes of leg movements.
Of course, wearing a skirt looks better, but you'd better lift it when you want to practice your movements. It's the same to buy a pair of trousers for practicing clothes. You can enhance your interest and confidence in dancing.