I would start by thinking of what type of things you like. Don't make a channel surrounding what others like. When first starting out (and continuing) you should make videos that you enjoy. For example, I like comedy videos, but I also like animation videos. So, instead of focusing on one or another, I make videos on both whenever I feel like it. What a lot of people try to do is fine one thing and stick with it. I personally do not think that is a good idea because t can get boring. Try different things. Try gaming; try comedy skits; try tutorials; whatever you feel like, try it. And, eventually, you'll find your niche.