There are 2 ways to boost your Youtube channel.
First you can make more than one account and start trading with other users on Youtube.
There are a lot of users on youtube that own more than one account.Mostly they make channel comments like this one '' TRADE SUBS''.
Also there are a lot of people that selling accounts so you don't have to lose time by creating them before you start trading.
The bad thing of this way is that you will have to spent a lot of time searching for users and make trades.
Second if you have money you can buy subscribers comments views ect from boosting services.I don't intend to promote the current web site but this type of services are called boosting.You can find various sites that will offer you from 100 to 6000 subscribers and more.
The second way is faster than the first one but as in all purchases on Internet you have to be carefull because you will come accross to a huge amount of scammers.
The decision of cource is yours and depends from the money and the time you have to spend.