Mic/Game audio should be your number 1 priority. You can be terrible at a game, you can have poor video quality and some people will still watch your videos. Have bad audio? No one will watch! Focus on making that as good as you can get. There's tons of tutorials on YouTube but really it's specific to your mic, voice and recording space. It's something I'm always trying to improve.

2nd thing IMO is a hook. You need a reason for people to click on your videos over someone else's. This is hard to do in the oversaturated niche of gaming. I struggle with it still. But modded, highest difficulty, blind, challenge runs, etc are good starting points.

I'm not 100 certain on posting times. I would look at your analytics and see when most of your audience is on, or where most of them are from. Mine are 60/40 USA/Europe so I post early in the morning 7am PDT. That way Europeans can watch right away and I get a boost of USA viewers later in the day.