How did you get subscribers for your channel?

I'd also say make a Twitch and stream on there occasionally too, and you can mention your YouTube channel to people watching. And as said above, using things like Twitter or Tumblr to promote your brand helps too. (My advice is, just don't go overboard with it. I've seen YouTubers where every ten seconds they're referencing their other social media, and it distracts from what you're actually trying to do, which is play the game.)