Oculus Rift Question

If what you're asking is can he play league of legends on a rift using a mouse and keyboard, the answer is kind of, but not really (I have a Vive, I'm just going to assume Rift is the same).

It's not going to be in VR, but you should be able to play any game in "theater mode" wearing the headset which basically means you are playing on an extremely blurry giant screen but again, it's not going to be VR. It's just going to be a huge flat screen. And I can't imagine anybody would really want to play League like that. I've only tried playing like that a couple of times and all of my experiences were terrible.

Don't see how it would be of any use for League.

There's a few good games for it and it's a cool experience but I wouldn't get it unless he has like 3 or 4 games minimum he wants to play on it.