You mean a Multi-Channel Network? If so, none. Don't join any. They will only take a cut of your revenue, own you for three or more years, and give NOTHING in return. Only if you're one of their biggest YouTubers will they do anything for you.
As for growing your channel, find YouTubers who are doing the same online game as you and are about the same size in subscribers. Propose to form a collaboration team with them and then do many (if not all) your videos with them. That is a PROVEN way to grow a gaming channel.