There isn't really a set network / best way to advertise your channel that is guaranteed to help you grow. As it does depend on the niche market that you are trying to connect with and what new things you are bringing to that particular field. As you said I definitely wouldn't recommend investing in Google Adwords or any system that promises you views / subscribers in order for a favour or money as this is against YouTubes terms of service and is very likely to get you permanently banned from monetisation.
The best, and safest way to grow your channel is the good old fashioned way of hard work and perseverance. Unless you are very lucky and create some viral sensation it can take weeks / months or even years to grow exponentially on YouTube, even well know YouTubers like Matthew Santoro grew very little in the first few years and then too off due to his hard work and dedication to his fans. All you can do is make sure that you are releasing high quality content, utilising tools which are at your disposal such as networking sites (Facebook, Twitter even Freedom) to build up your social group, and releasing on a schedule so user come to know when to expect a video from you.
And finally most networks will only offer you a chance to grow, such as Freedom by providing you tools to use, and a place to network, as they will ultimately leave it up to the content creator (you in this case) to take that initiative and try and push your channel forward, unfortunately no-one else can do that for you.
