Well firstly the ads that are going to be displayed on your website or blog will intirely depend on how well you have optimized your site and what keywords you have optimised for.

Now with Google adsense you have no control over what is going to be displayed on your site, Google chooses for you and they choose based on how well your site is optimised and for the keywords advertisers are paying for.

Say you have a site about Cars and the main topic on your site is Fast cars, you will most probably get every ad that people have bid on for the broad keyword car.

If you want a specific keyword to show up like "Expensive Cars" you will have to optimze the page for that keyword.

Example: Main Keyword in Main Titles = Expensive Cars,

Heading = The Worlds most "Expensive cars"

The keyword throughout your content at least 5 times

"eg, I love my "expensive cars", the most "expensive car" i have seen was a Lambourgini. One day i hope to purchase the worlds most "expensive car" and drive it home to show my husband and kids. I really want a expensive car leave me a donation so i can get 1."

Domains don't really matter just as long as your titles & content have the keywords you want in them, ohh I almost forgot also make sure your meta tags have the keyword/s in them as well.

All in all the keywords you are optimising for should show the results you want in the ads that will be displayed on your site.

I hope this helps, ICANDY :)