avoid sub for sub. It does not give you subscribers that are interested in the content you post. Its the worst way to gain a following. What good is 1000 subs if you only get 10 views because of the fact you got in random peeps with no interest in your content what so ever? id rather have 100 subs with 50 views, cuz that will get you much further in the long run.
dont get me wrong, im no pro at all, as i just started on YouTube myself, but sub for sub is bad. Just think about it.
I use Facebook groups to share video's and try and attract new subs that way without asking for sub for sub. That way, if someone from Facebook subs, they are actually interested in what you offer.