I spent many years learning how to shoot, edit and deliver video with sound that is clear and easy to understand.  I am the expert in recording great sound for video at events.
Even with low cost gear you can get good results, if you know how to use it right. My purpose is to provide others with information that will allow them to record sound better so that, when it comes to editing or delivering the videos they produce, they will have the best audio possible.

Two things to start with:

1) Always monitor your sound from the recorder’s (usually a camera) output. Wear (closed cupped) headphones that block out as much sound as possible the whole time that you are setting up and recording. By focusing on what the final sound is going to be like, you can tell if it is clean or noisy, loud and clear or quiet and dirty.

2) Avoid using auto gain. Many cameras have a function that adjusts the audio recording level based on how loud it is. At first blush this seems like a good idea, it makes the quiet stuff louder but keeps the loud stuff from overloading and getting distorted. The problem is that it doesn’t distinguish between noise and your desired sound source. What ends up happening is you get a bunch of room noise (or background sound) on your track and every once in a while when the audio you want to record is loud enough, it sounds good.
A better choice to get a more professional sounding recording is to manually set a level and listen to it (while watching the level meters) to maintain a consistent signal with natural dynamics (loud and quiet parts).

Let me know if you have any specific questions and I’ll do my best to answer them.