As twilight said when making videos on a new channel it is important to focus on games which are not that big on the YouTube scene, as many of the games which are already covered by much bigger channels, and it is very unlikely you will find someone from that channel switching to yours, as there are used to the bigger channel and see no benefit in changing. I recommend starting out on either small indie games or online web games (ik), as these have the least amount of channels uploading them. Here you will find growth a lot easier than in the CS scene for example, sure you can try CS, and maybe you might see a growth in your channel, but generally speaking you will find it a lot easier growing from a smaller less populated game than a triple A title.
