I have considered doing one for fun, and although I have never pulled the trigger on it I do have some insight into what
I would do were I to start.
1. Pick a game that is coming out and focus your entire channel on that game. You can branch out later, but if you want to grow your channel you want to start with a laser-focused target audience.
2. Get
real creative with your approach. You can be
the Authority on the game and help others with tips/tricks and advice as to how to do
everything in that game or you can have an entertainment approach. If you go with the latter you really need to figure out something unique that will set you apart from the rest of the pack.
3. Lean heavily into your personality. There are a lot of options out there for who viewers are going to want to watch play this game. They may find you because of the game, but they are going to
stay (i.e. subscribe) because of your personality.
4. Get creative with your marketing. Go hang up fliers around town/school/Gamestop etc. Buy a $12 ad in the local newspaper. I would buy a stack of ad-card and put them in the table-top holders at the bars around town. Put a sign in your front yard and one of those magnet ads for your car.
These are just a few of the things that I would suggest off the top of my head, but I did write an entire article on this subject a while back. In case you are interested:
https://community.tubebuddy.com/index.php?threads/35932/