You need to get a "funnel" video. I don't know what the correct term is but, what you need to do is capitalize off of the release of new highly anticipated games, and then be the first to make tutorial/how-to/tip videos, showing how to do stuff that everyone that gets that game is going to want to know right from the start.
IE. - I made a video within the first few hours that GTA V was released, showing where the airport was, and how to fly a jumbo jet, because I wanted to know where the airport was myself, as the map was blurred out until you had actually discovered that part of the map by driving through it, and I knew so many other people would want to know the same thing.
I do not really consider it one of my better videos, but it my most viewed video, and has gotten me hundreds, if not thousands of subscribers.
It currently has almost 550,000 views.
That video introduced people to my channel, and then other content of mine began to get more views as-well.
edit: Also, tags are really important. Had I not tagged the video correctly, I probably wouldn't have gotten nearly that many views. What I try to do, is think up pretty much every way that someone could search "gta v how to get to the airport". I also add a lot of tags to my description, although I'm unsure of whether that makes a difference.
But yea, tagging it correctly got me as the number 1 search result on youtube for "gta v airport", and pretty much any other variation of those words that you can think of.