What does that have to do with filmmaking?
Your movie is only as influential as its ability to spread.
If nobody knows about what you're doing, it doesn't exist.
Here's a good general rule:
Your advertising budget should be double your budget.
If everything is well executed, you should realistically profit 50% of your total budget.
This formula is based on historical trends.
So if you're making a movie for $1,000, expect to spend an extra $2,000 in advertising in order to gross approximately $4,500.
However, if you spend only $1,000 to make the movie, you will be hard-pressed to make back a dime.
Or if someone gives you a set amount, say $10,000, to make a movie, then consider spending about $3,000 on production, and the rest on promotion.