For gaming stuff, I would be very hesitant on collaborating with other folks I did not play a few things with first. I would rather have witty banter, and busting each others chops during game play to make it funnier. Doing a collab just for the sake of trying to build an audience out further will give you way less in the long run, than doing a collab that is engaging, funny, and enjoyable to watch between two folks who enjoy gaming together.
I have seen a few collabs like the first one I mentioned above, just doing it for the sake of doing it. After a few minutes it was just dull and painful to watch. Right now if I do any sort of collab, it is going to be with friends of mine who I just want to game with. They don't do YouTube stuff, but even so, just having others in my video and hearing the conversation between us will be entertaining because it is more natural.