well if you commentate live (like lets plays) then i think maybe your natural reaction to whats going on would be best and most engaging for your viewers. but if you're not into that style of gaming commentary then maybe try talking about yourself and stories about you involving video games. A great youtuber i watch called AshozGaming does these things called TopicTalks, where he picks a topic (usually related to recent news in the gaming industry like the latest patches for games, new platforms etc and that really gets his subscriber base involved
he only has like 250 subs, but it really gets his channel feeling like a community, maybe you should try that!