There is definitely no need to pay extra for the videos and tutors. Everything is written for a ninth-grade reading comprehension and all the concepts are kept quite shallow. No critical thinking is required to pass with a 90% or higher in all the units.
The vast majority of the theories and pedagogy are only discussed in a sentence or two, so you don't get a very rounded perspective on teaching ESL. There is only one method that is used in any detail, so that you feel you have no choice but to use that method in your own teaching because it's the only one you really understand.
If you already have a strong command of English, just be aware that the grammar and the poorly-aged content can make the units a bit of struggle. The materials clearly have not been updated in a decade or two.
Some of the units will make you do your own research because they don't cover it, but still require you to know it. This includes having to read a downright offensive piece about judging a culture based on its masculinity level (femininity is not a part of this piece as they take the view that femininity is simply the far low scale of masculinity).