Should my Youtube channel be only Minecraft or alot of different Games?

It all depends on your focus - if ou have a lot of games you wil get a lot more followers and views and intrest and stuff. But if you have one game (ie minecraft) you have a lot of time to create a whole complete channel about the game wich wil atract a lot of minecraft fans - its all your choice

If I were you, I would record what you enjoy the most. The best lets play youtubers or tutorial writers attract a lot more attention when they do more than one thing. Markiplier, a great youtuber in my opinion, is one of them that has expanded his games on his channel. This keeps me constantly entertained and hooked on his work. He also puts out his own great advice on how to get started and do well. He's encouraged me, even though I haven't done anything yet.
The bottom line is believe in yourself, and play the games that you enjoy. That's what he did- and that's what I hope to do, as well.

Just create sections there. Like VEVO. When you enter there, you see, the music section, the actors speaking or something like that. You can create sections like for example, GTA, Minecraft, Call of Duty, etc.

Have multiple channels for each one.