In my opinion, it's not so much about how much traffic you get, but how many fans you have. You need a following, not just a swarm of people who may or may not be interested in what you're offering.
Here is my rattling, it is not about quantity, it is all about quality traffic. Your niche ought to be specialized, demanding and definitely helpful before anyone shares same sentiments. Once your foundation is there, do seo on respective niches and forums, and watch revenue coming! Hope It Helps, Commoner
What do you sell, what service do you offer? Etc... It depends on what you do. I run humor sites, so for me to gain $4k, I'd need a lot more traffic than someone who sells tshirts or offers other things.