English courses and self-study

What general English courses including for self-study for each level can be most helpful to learners? I’m trying to explore this issue. Do you have any opinions in this regard?

Sure I do: How to learn English? (30/30 Challenge)[YSaerTTEW443543]

TOEFL listening lectures: Why do Birds of Paradise have amazing plumages?[YSaerTTEW443543]