I'm doing it all manually. That way I can cherry pick articles to may liking and also spice up the headlines if need be.
Manually - Labor intensive and you might not make enough money to cover those time
You have google adsense - are you sure they don't have problem displaying ads on news aggregater site that doesn't have any original own content?
Look at other news aggregater sites like one of my favorite
http://cryptopanic.com and try to implement feature they have in yours.
Good luck