There is no doubt good audio is important. If you do nothing else while recording , make sure that the sound is of good quality and clearly audible. Poorly designed slides can be minimsed or a distracting camera shot hidden but the audio is the most important.
The environment in which you are working and the type of presentation will affect what kit you may use. Below are a few examples but first a very quick overview of the different microphone types to try and help explain the difference: Cardiod microphones will pick up audio from one direction and will be quite effective at rejecting audio from behind. This is good in an office or studio environment as hustle and bustle will be minimised. An omni directional microphone is great for groups and multi person environments where audio could come from all directions. In a lecture capture environment, a boundary microphone is usually best, this will allow you to move around the desk a bit while still capturing the audio.
What to buy?
Media services have tested various types and brands of USB microphones to try and make some informed recommendations. Quite often the mic and camera built into your computer monitor will suffice, it is worth testing with them first. Below are our choices, there are of course hundreds of other options available:
Recommendation 1 is the Beyerdynamic MPC70 is a high quality USB microphone with on/off switch. It has a broad pick up pattern and rejects class noise well. It would be on the upper price range at around £250. https://www.amazon.co.uk/Beyerdynamic-Boundary-Microphone-Keepdrum-Extension/dp/B01H57T5XS/ref=sr_1_2?s=musical-instruments&ie=UTF8&qid=1473243633&sr=1-2&keywords=beyerdynamic+usb
Recommendation 2 is a cheaper alternative to the first one, its the CAD U70. With no buttons or switches to worry about, the microphone is simple to use, however does not produce the same quality of sound. The price does reflect the quality a little but for occasional use this is a cost effective microphone. Around £40.00 http://www.guitarcenter.com/CAD/U7-USB-Desktop-Boundary-Microphone-1273887994631.gc#productDetail
Recommendation 1 is the Blue Yeti microphone. Some have claimed it to be the ultimate computer recording tool. This microphone is well built and comes with its own integrated stand. The audio quality is excellent and allows a set of headphones to be plugged in to monitor the sound. The other very useful feature of this mic is that it can be set to different modes depending on what scenario you want to record. very flexible, highly recommended. Information here: http://www.bluemic.com/products/yeti/ and around £100.00 on Amazon https://www.amazon.co.uk/Blue-Microphones-Yeti-USB-Microphone/dp/B002VA464S
Recommendation 2 is the Audio Technica AT2020 USB. This is a very high quality microphone from a very well renowned brand. Comes with a desktop stand, pouch etc. the advantage of this over the Yeti is its size, it will be much more compact. Again with headphone port and volume knobs. A little more expensive at around £150.00 https://www.amazon.co.uk/gp/product/B00B5ZX9FM/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A3P5ROKL5A1OLE
Recommendation 3 is much more cost-effective and great little microphone for the money. The Blue Snowball is a compact mic, complete with stand, cable etc. Comes in at around £50 and should cover most desktop applications. https://www.amazon.co.uk/Blue-Microphones-Snowball-iCE-Microphone/dp/B006DIA77E
Good quality headphones will allow you to monitor and review your sound. Don't need to spend alot for these purposes but something more than iPhone earbuds may be useful. https://www.thomann.de/gb/behringer_hps5000_2.htm?ref=search_rslt_headphones_384433
A swing-away desk stand is a good way to reduce noise on recordings from knocks on the table etc. This one is of good quality at a low cost. https://www.amazon.co.uk/Keepdrum-NB35-WH-Microphone-Microphones-Assembly/dp/B01AUMQYRK/ref=sr_1_3?s=electronics&ie=UTF8&qid=1473244783&sr=1-3&keywords=Keepdrum+NB35
Using a camera is not compulsory, however can be useful when you want your viewer to be able to identify with you, especially for students you do not know in person.
Recommendation 1 is the Logitech C920 HD Webcam. It is very well made, has a good length of cable and appears to be widely compatible with devices. It has a good field of view and produces great images. Not only that, its sound quality is actually very usable too. Price varys on the internet but usually around £50. Well worth spending that little extra. https://www.amazon.co.uk/Logitech-C920-Pro-1080p-Webcam/dp/B006A2Q81M
Recommendation 2 is the AMX Sereno. This camera has got a really wide field of view and is great for capturing images where there may be more than 1 participant such as at a boardroom table or at a panel discussion. Its audio is very good too. It is a little pricier though at around £120.00 http://www.amx.com/sereno/
Either of these cameras will work well in a lecture theatre or at an event. The addition of a floor stand such as this one https://www.thomann.de/gb/km_201a2_schwarz.htm and a USB extension cable would be all that would be required.