There's a lot of good advice in this thread. However, a lot of it depends on your being able to
make the game you're designing...
There's a lot going on there, so let me explain:
- People with core development skills, ideas, and no GDD might make their dream game, but it's unlikely (or it won't get finished, or it will suck, or...).
- People with core development skills, ideas, and a GDD are significantly more likely to make their dream games work.
- Nobody who doesn't have any core development skills makes their dream game.
Right now, it sounds like you have ideas, and are working on a GDD, but don't have core development skills yet. The GDD helps, but it's not enough. You
need to have skills to be able to make your game. An idea alone, even with a GDD, is not enough.
You might think that you can just get other people to make your game for you. Or at least hope that's the case. From a physical standpoint, you'd be right. From a practical standpoint, it won't happen. If your vision is to have a studio make your game, I would suggest reading this killjoy article from last week's Escapist:
Why Your Game Idea Sucks. (Edit: I should note the preceding article is poorly titled, and the point is not to dismiss your idea, but to emphasize the futility of pitching an idea to a development studio, no matter how brilliant you think it is.) Then listen to
Electric Funstuff's The Next Big Thing for a musical horror story on why you probably wouldn't get the game you have in mind anyway. Similar principles apply to cobbling together an Indie team if you don't have skills to contribute yourself; you won't be able to find sufficiently skilled and committed talent, if you're able to find any at all, and they won't accept your directions either way if you aren't part of the active team. A GDD won't change that.
I mention only coders and artists in my diagram, but you can bring pure designer skills to the table and still be in the blue circle. However, while maintaining a GDD is a big part of a designer's job, that won't get a game made. You need to be an implementation guy, not just an ideas guy. Maybe you can build the game in Game Maker or RPGMaker. Maybe you can make mods for the Unreal engine or the Source engine. The basic idea is that you need to be able to
build your game, given the right tools. You'll need only minimal coding/scripting and they'll provide some art assets for you. But you have to be able to at least do that, or your idea will inevitably suffer in video game purgatory, and never get made.
I don't want to dissuade you. Anyone
can make video games. But you must do a lot of game making yourself. There's no real way to make your idea happen on other people's skills alone. If you don't have the skills yet, you need to learn them and use them.