Skype requires only 1.5Mbps/1.5Mbps for both download and upload speeds in order to achieve satisfactory performance. To have an uninterrupted video call with clear sound and image, one may need higher download/upload speeds. Sometimes, a Skype connection is simply unstable due to other factors, i.e. the weather, the server and so on. One cannot say absolutely the ideal Internet speed in some of these cases. I suggest that students conduct a Skype video call with family or friends to ensure the connection is good enough. On SpeedTest, you can test your current Internet speed. The bandwidth I am currently using here in Taiwan is: Download Speed 300 Mbps/Upload Speed 100 Mbps.
You do not need to have a speed as fast as mine in order to have Chinese tutorial lessons. A long-term student of mine located in Canada uses 25 Mbps/10 Mbps. Another long-term student in Italy uses 30 Mbps/3 Mbps. Our lessons rarely have any connection issues. It can be helpful to use wired Internet rather than wireless Internet during Skype video calls. Wired Internet simply allows the connection on your computer to be more stable, for you are not replying entirely on the wifi signal.