Here's some ideas:
1) If your channel with the school is still up, post a video promoting your new channel on it. Give a link to your new channel both in the video and in its description.
2) Unless the school owns the channel (and thus its videos), copy all your videos and post them to your channel. Post them in chronological order.
3) Go after a niche. No, gaming itself isn't a niche. What genre of games do you most enjoy? Focus your channel on that niche.
4) Name the channel after yourself. YOU are the channel. What's your first name or nickname that you wouldn't mind being known as? Add the game genre your channel focuses on to that name. For example, "Jack RPG". But make sure no channel already has that name. If someone does, pick a different name. It needs to be unique for you to stand out.
5) Are there YouTubers near you? If so, contact them to do a collaboration video with them. No, it doesn't matter what their channel is about. Just have them on your channel gaming with you. You then appear on their channel doing what their channel's niche is. If it is a beauty channel, that's fine. Let her slap you up with make-up. While she does, you two can talk about your channel. Just as you two will talk about her channel for the video that will appear on your channel.
6) Invest into a really good microphone. Your camera doesn't need to be great since you'll just be showing a postage stamp of yourself in the lower left corner playing the game.
7) Always ... ALWAYS remember that it is YOU that is your channel. Talk, talk, talk, talk, talk. Do NOT think anyone cares about how good of a player you are. They don't. There are always better players than you. People subscribe to hear YOU. Let them hear you. Don't ever go silent in a video.
Good luck!
