The short answer is the audio is more important to your video than the video is to your video. We can struggle through bad video quality if the sound is ok. Bad sound quality on the other hand is unbearable. And people will abandon whatever content you’re sharing if you have bad audio. So that answers that question.
If you want to have good sound, first accept the fact that those old videos you made with bad sound are bad. And that the reason no one watched them is because of the bad sound. Let go of the humiliation, and move on. It’s easier said than done, but this is the world we live in! It’s really a lot easier than you think, and it’s best to just keep moving!
Next, I’d say one of the most effective and least expensive ways to correct bad sound in your video is by understanding how sound bounces off of hard surfaces and creates echoes. Just hanging some blankets on walls, or stuffing loud corners with pillows could do the trick. Understand how your proximity to your capture device influences the finished product too. The sad truth is you need to be kinda close to capture equipment to sound good. And if you’re in a pickle trying to decide which is more important, the shot or the sound, remember my words. They will abandon your content if it sounds bad.
Gearing up on good sound equipment, and developing your audio repertoire is a journey. And you don’t need to do it all at once. Good fundamentals will help you scale naturally. A good shotgun mic., and desktop mount are adaptable, scalable options. XLR mics generally sound better, but will require an audio recorder like the Tascam DR-40x. By the time you’re looking at recorders, you’ll be well on your way to having better sound.