First try to learn the basics:
Making simple rooms.
Train your entity placement skills.
Aswell as your lights placement...
Then try to make a simple level....
So not a whole game.
But just to learn the basics.
Like making a room that is based on a theme.
And a door that leads to another room, dont know what? You could make up something.
After that, try to make some more complicated levels.
By editing the huds, skies, fogs, light colors.
If things will be dynamic or static.
Where the enemies will be placed.
Maybe some scripts for certain events.
And also try to make your own textures...
Or maybe even models.
And after that, you could begin your "first"? game.
Making a thread with screenies of course.
And a story line.
But remember, even if you can handle all the basics...
or maybe the somewhat advanced techniques with FPSC.
A good game isnt allways about the graphics or level lay-out.
The biggest thing that you need to worry about is the story.
Hope this helped!
Cheers,
Cheese Cake.