If I could start over, with the knowledge I have now, I would also invest a lot more time into SEO. It seems to play such a huge, significant role in a channel's success that starting over with a solid foundation and understanding of SEO would go soooo far into launching a successful YouTube channel.
Also, starting over, I would spend a lot more time learning how to use not only hardware but software. I have found myself spending a lot more time recently looking into using both the hardware and software I own.