Well, for starters, if you think the commentary is horrible, DON'T post it. Only post ones that you are satisfied with, because if you are, then your fans will be too.
Though, since I'm not a live commer like you, I haven't got that much advice except balance out your focus on both the game and what you say. Maybe, don't start moving until you finish and do your intro well, or if there's no need to talk (in a pressuring clutch moment for example) then don't talk at all.
Also, watch other Youtubers who do live comms as well, and get some tips from them. A good example (for me) is youtube.com/user/ImAnderZEL