xSpirit actually mention some amazing ideas.
But I suggest going back to the basics before you want to do a full length 3D game.
At my school I do CreativeMedia and we use a website called Codecademy (https://www.codecademy.com/). The lessons are only about 5 minutes long, but they are really easy to understand with structured out hints along the way.
I suggest using this other than a 3D coding kit so you can actually understand the basics and not be confused as soon as you start.
Yes, it does teach you how to make a website. But from experience I've learnt that it's easier to start of with the basics, (Making a simple website) then continuing onto making a game.