How much are 1,500 unique [UK] visitors per day worth?
How much money could you make per month if you optimized everything?
Either I am too stupid to use tradedoubler or it is not very good, a couple of pounds per month. I hardly makes any money. Adsense is better, a multiple of that. CJ is even worse than tradedoubler, about 10 cent per month.
Then targeting is what you need to work on. Showing ads to an untargeted audience will sometimes work because of random luck, but the tighter your targeting the more productive your promotions will be.
You can do this by hunting for ads/products that relate well to your content, or you can choose ads/products based on who you think your audience is and what their mindset is likely to be. You can sometimes rule out some products for that reason, too. If your content attracts people looking for something free, or very young visitors, you won't sell much to that crowd. Try to discern whether your visitors are generally male vs female, teenage vs. middle age, techies vs treehuggers, etc etc. and you'll have a better idea what to advertise on your site, and also how you might develop new content.