In Blogger you can choose from different templates, or you can find some on the net to use inside Blogger.
Search for Blogger Themes or Templates in Google.
You should look for simple themes. Simple themes bring in more money.
Never choose a black background behind white text. It's so hard for the eyes to read, and it's also a signal of a different type of site, like a Goth site, Hard Rock, World of Warcraft etc. A light background and dark text is better.
Wow, I just found this on a search: http://www.eblogtemplates.com/ads-theme-blogger/
I know what you are thinking – this might not be the most pretty template out there, but we do not care about a pretty site, just a nice site that bring in money. It actually has room for ads in the right places and in the right format and size. I'll definately use it myself on a blogger blog.
The theme/template should never steal away the interest from the content – the text and the ads.
More about ads later, but one golden rule – make them invisible. They must not stick out from the surroundings. Don't worry too much about it now, I'll tell you more in a lesson. Or if you have $10, you really should get the best book there is on the subject, print it out and read it. I did. I went from having earned nothing or almost nothing for 4 months, to earning $3 per day, later moving up, up, up, and now it's between 35-40 dollars per day. Mostly thanks to this book. And at that time, I actually payed $97 for the book, but only regretted one thing: That I haven't done so earlier!
You'll find the book here, if you are interested and can afford it: http://www.netpenge.info/anbefaler/adsensesecrets – it seems it's for free now, but I'm not sure of which conditions.