For low-cost public transportation in Turkey, you can apply for a Student Istanbul Card. In order to apply for this card you need have your YOK number, given by the Student Resources Office( you can get it also International Relations Office). Then you need to visit İETT İşletmeleri Genel Müdürlüğü Elektronikkart Yönetim Müdürlüğü Karaköy/İSTANBUL (Near Tünel).
1-) YOK number
2-) Student certificate
3-) Passport and copy of passport
4-) Fee of the card