As a marketing professional, I'll be the first to say that it's unwise for a business to overspend on their marketing.
How much to spend is something I've talked about before, but even if your budget won't get you a dream strategy, you can still grow your business by following these important steps:
For Details:
http://www.newmarkstudios.com/blog/what-to-do-when-your-marketing-budget-is-tight
Build a Better Marketing Budget
http://www.newmarkstudios.com/blog/build-a-better-marketing-budget