You're being too ambitious too early on. Get some pocket money, buy the regular latest version of 3DGS and a book (that can be purchased on this site) called The Official Guide to 3D-Game-Studio.

I warn you NOW.. Game design is NOT for the impatient. It is NOT a cakewalk! It takes time and effort. That is the first thing that you must come to terms with before pursuing game-design. You will not become a millionare in your first year of game production. You will not be able to make best-selling games without a good team. You WILL, however.. Be able to express yourself with it.

Game design is an art, not a way to make money. Mentalities such as this are what seperate games such as American Mcgee's Alice from games like that Hannah Montana version of guitar hero. It seperates good games from cheap knock-offs.

You are currently thinking too big, an overambitious project is destined for faliure, why? It's simply out of your reach.

What you should do first is throw away the mentality of "I wanna make a game". It's too ambitious at this early stage, and it is rather blank.

Some thoughts you might want to include:

"What genre is this game going to be"
"What type of setting is the game in?" (fantasy, war, etc)
"What mood are we trying to give to immerse the player in this virtual world?"

"What will it's key features be?"

^
This question is where you need to be VERY careful, you don't want to be too ambitious. Settle for something that is at or around your level. And pick it together one small piece at a time, remember.. World of Warcraft wasn't made in a week. It took years to make, test and and appeal to. If you are impatient, you will never be sucessfull in game-creation.

Also, you don't to add too many little features that have little to no relevance to the actual game. This is known as 'feature-creeping' and is best avoided.

An example is World of Warcraft (The Lich King expansion), they added new veichles (which turned out to be mechanical). The idea of an unpainted metal motorbike did not fit in with the frozen tundras of Northrend. They just wanted something new, but added little relevance to the actual atmosphere. Basically, if you are going to add a feature; add one that is relevant to the look and feel of the game.

You don't see goblins in Runescape with Uzis, now do you?