The usual way for a screenwriter who wants to get his script on the screen leads him to an agent or producer. And that kind of people follows a simple logic: The more unknown the writer, less probable the success of his script. As a result, it seems better to invest less in a newbie, as the return on this investment is not guaranteed.
To bring it to the point, there is a disproportional growth between the costs for getting the script on the screen and the likeliness of an aspiring screenwriter to get this done. Although writing itself costs little more than time and ideas, the budget of the film is to be kept low if one wants to increase chances to get it on the screen.
Keep your scripts within simple settings, at least at the beginning!
Other factors to be taken care of are the costs of marketing your script, research costs, maybe travelling costs to get in touch with people, and copyright costs.
