I have several sites with adsense on them, but one small site, which accounts for only 1% of my total page views, returns 20% of my total adsense revenue. Problem is that the niche is so small, probably less than 200 people on the web are seriously interested. Maybe another 20 per month are mildly curious. How do I expand this site? 1. Blend it with another related niche? 2. Start a forum? (Which I don't know how to do, yet) 3. Add more pages? (I can probably double the size by adding a picture gallery) 4. Just be happy and move on to the next.
start a forum , and once it gets spidered on the internet, you'll be surprised , people looking for your niche will find your site
How many of those are already visiting your site? If you have the market cornered then adding pages for the sake of it won't achieve much. A forum would be a good idea as it would give you a better opportunity to interact with your visitors - they may well give you ideas for diversification or expansion that you hadn't thought of yourself.
Some niches hae very little traffic according to overture. Unless its a very specialised niche that is bound to get you good rnkings becauasewe of low cometin, I don think its worth starting a site. Of course, it might be that you are very knowledgable in it the subject and can write some quality stuff on the subject.