Lighting is the definitive border between the amateur and professional.
Regardless of your budget, you are obligated by the office of “filmmaker” to light your project properly. People who say ‘lighting isn’t that important’ are simply justifying their lack of artistic ability. Abandon them to their failed project.
Lighting is all! It is the very mood of your film and without it, nothing else will matter.
Again, study the great painters and observe the play of light and the fall of shadows in their work.
If nothing else—if you don’t understand the technical points of proper lighting—get screen shots from other films with lighting you like. Arm your Director of Photography or Lighting Director with references and he will get as close as he can with what he has.
Be a child of light.
Darkness is boring.