Audio: As you go along you may branch into audio processing etc, but I hope you feel good about where you're at with this. Actually, thinking about this some more, since your product is really auditory, perhaps you'll be looking into audio equipment and options sooner. https://www.youtube.com/watch?v=vc46lG8EC7E looked decent for some tips. There will be others. Are you doing this with live interviewees, in your home/space? You could mic things up like the Joe-Blowhard-Rogan Experience, Howard Stern, what have you, or go for a boom mic for more ambient sound. If you're doing these remotely, you could use something like Shotcut to embed their frame in yours or vice-versa.
Elgato Wave 3 - USB mic
Pop Filter
Swing arm
Shock wave mount