Buy books and tapes 100-200, and download audio online.
Depending on which city you are in, Beijing and Shanghai are a little more expensive, about 1000, but there is not much difference between the grades of 300 and 500 ... There are also videos downloaded online.
If you don't do your own research, the online fee and electricity fee of 100 will be enough when you buy books and download materials ... anyway, the certificate is useless. ...