The other thing I’d suggest is a good pair of closed back headphones for the operator to wear. So they are listening to what the mic(s) are actually picking up – not the ambient sound in the room. It then becomes obvious is a fridge motor, AC unit, plane overhead etc is adding unnecessary background noise. Also watch the audio level meters (most cameras have an option to show them as an overlay).

It’s not worth paying over the odds for ‘prosumer’ lapel mics, anything ending in an unbalanced 3.5mm mini-jack is limited in quality. Only if your recording device has balanced XLR inputs can the quality of a better mic (&preamp;) be noticed. A cheap $20 mic will be easily good enough for recording a piece to camera in a closed room with little background noise if used properly.

So if you’ve got a $200 budget spend $150 of it on the headphones and only $50 on the mic!

Even the best kit will give appalling sound quality if you don’t set it up properly, and most common mistakes can be picked up just by listening while you’re recording.