Hey Daniel,
As Greg suggested, use a green screen when recording yourself + make sure to have plenty of light both on your and the green screen, to get a better key. And, don’t wear green!
Not sure why you want to use AE for this job?
There are plenty of faster ways of doing this, that will give you the same quality, if not higher.
When I say higher, as an example, if you use PPro instead, you’ll have much better audio controls.
One big feature that will save you time is to use Auto-Ducking, so every time you speak, the game audio will fade down to let your voice come through.
Same goes with syncing audio and video up.
And, yes, you can do chromakey, create masks + Zoom/Rotate video in most editing software packages too.
My advice is as you are starting out on this new exciting venture, is not to over-complicate the production process before you have even got started, but instead concentrate on making engaging content.
Atb
Mads