have you looked at using locations in your keywords like the city you live in? You would of course have to research if it gets hits, but it might not have any advertisers there
Hi I've run Adwords for 5-6 years now and I'd say 2 things. 1. It is very niche dependent, it's a direct result of how many other advertisers are out there. 2. In a competitive niche try using long tail search terms, in a very competitive niche they'll have to be very long!! If budget is your issue which I'm guessing it is, then you'll have to limit your exposure to a few terms that give you a return and allow you to keep within your budget. Hope that helps.