Are your courses just slides, or are you planning to stand up and deliver your course with videos?
If you're happy with sitting down at your laptop or desktop computer and recording, this is fine. However, this is mainly for screen-cast recordings. If you want to stand-up and deliver your content in a more interactive way, then I suggest you buy a good lapel microphone (Boya M1) or a Zoom H1n.
With the lapel microphone, you can plug this into a DSLR and then adjust the volume/gain settings through the camera. This is really handy if you don't want to hold a microphone.
With the Zoom H1n microphone, you can actually use this as a USB microphone into your laptop or desktop. The audio from this microphone is high quality, and it also works for screen-cast.
It's really worth investing into good quality audio and video.