Although I hate to say this but it's much better to grow your subscribers organically than buying them in various service providers. The process is going to take a long time for you to build your subscribers organically, but at least they are very targeted.

Start off by joining gaming groups in social media channels like Facebook, Twitter, etc. Also ask your friends if they belong to a GC full of Youtube gamers whether pre-recorded or live for you to share your video. You've got to be consistent in creating content on Youtube.

And if you have some spare cash, try hosting a small giveaway in exchange of letting them subscribe and follow your Youtube and other social media channels. The journey is not easy, but it's gonna be worth in the end.