I'm recording episodes of my new podcast, speaking on front of groups of around 200 people and getting on a lot of conference calls and I want to develop that charismatic and influential voice that exudes confidence and authority.
Game walkthrough comedian Markiplier had his voice deepen considerably over the past couple years.
Don't concern yourself with his CONTENT; find a video from 2 or 3 years ago of his and listen to his VOICE...then listen to a recent video to hear just how much it has changed.
You obviously don't have two years. But merely by talking consistently will exercise your vocal cords and result in a deepened, stronger voice.
A vocal coach is a paid option.
Youtube searching for "how to improve my voice" came up with a bunch of video results.