Have you optimized your site for SEO?
Depending on your level of traffic, you may have to invest some time and money into growing your traffic levels. If you're not optimized for SEO yet, I'd spend my initial dollars on organic Search Engine Optimization, so that you begin to grow traffic to your site. You gotta get traffic before you can start making money from your site visitors.
If you're only making money from ads, and not from your site services, you're going to need significant traffic numbers before ads will start making you much money. This is especially true because your website doesn't seem to be targeting a niche group of people - and this means that it will difficult to get very high click through rates/conversion rates, since it will be tough to have targeted ads.
For this reason, I think you should focus on growing your traffic at this point. You can probably get optimized for about 5 reasonably competitive search terms within 6 months. A competitive SEO guy will cost you $2000-$2500/ month, and you'll probably have to pay him for 4-6 months in order to be successful.
If you don't want to spend that much money, I recommend learning about SEO yourself. There are tons of free blogs and free software that will help you, as well as premium ones that are even better. I think that SEO is really fun, and its very satisfying to see your site traffic increase as you improve your search engine rankings.
Here are my favorite free tools:
Here is my favorite paid tool - ($99/mo):
One last thought - are you tracking site visitors and their activity? Google Analytics is very good for this, and it is also free.
Hope this helps!