Personally the fastest way to get me to sub to a gaming channel is to have well thought out and funny content (I.E. parodies, animated stuff, reviews, or the kind of thing jontron, PBG, HVGN, AVGN, ect. do) and I think lets play commentaries work so much better when there is more then one person. Having another person takes some of the pressure off of being entertaining and playing at the same time, while also giving you someone to bounce thoughts off of to keep commentary interesting. I think the lets plays that are really successful are successful not from the game play but because they like the person or persons commenting. So if you have trouble doing good commentary on your own think about collaborating and doing co-op/VS stuff until you get more experience and more comfortable.
Most important though just make sure you value quality, and please edit when needed. There are thousands of gaming channels and too many of them lack editing or structure. Don't waste the viewers time with the menus and opening loading screen if there isn't commentary, edit that kind of stuff out. It sounds small but when you have as much competition as there is in the gaming channel business every bit helps.
But yeah just be yourself, value quality, and have fun, that's the best advice I can think of.