If you have an idea for a film story and it takes you longer than say, 2 or 3 sentences to sum up on paper, consider doing something different. In my experience, a convoluted narrative is best left to those with the ability to pull it off.
The term "high concept" means an idea that is very simple and can be summed up in very few words. This is what you should consider when on a limited budget.
Don't think of it as formulaic, but rather - "focused."
Having a basic premise does not mean your story has to be "basic." You can have a distinct premise with which to base your story on and all it means is, you have a sun for your planetary story elements to revolve around.
Here are some examples of successful "high concept" Indie films that were possible on small budgets:
The Man From Earth
The Blair Witch Project
Lost in Translation
Your characters can be complicated and have depth, sure, but try and keep your story well-defined, interesting, and entertaining and you just might have something.
©2012 Chris Santucci