Audio: Search Amazon for "USB Cardioid Condenser Microphone" to find a suitable microphone for doing interviews, webinars, etc.

Here's two that we use: Audio-Technica AT2020USB+ and Neewer CM25

Lighting: Make sure your light source is behind your camera and pointed at your face. Any bright light shining into your camera will create a backlight effect and can make your background look washed out and you look like a silhouette.

If you need a good lighting option, a simple desk lamp behind your camera can work. Or, depending on your camera setup, a Conferencing/Webcam light might be a good solution, or just a simple ring light could work as well.