I think it's perfectly doable. I don't think any of the content is too difficult.
First, download the syllabus and order a revision guide from your exam board. You can use the revision guide to take notes from, and the syllabus to tick off what you've done. That's really all there is to it!
I think Geography is easy enough to teach yourself if you find it easy already, yes. And if you don't understand something there's always videos online.
Good luck~!