I have a website and bought several domain names?

[Ragde]

I have a maim website with a domain. But I wanted to also register more domains to redirect them to the main website so that it will have more search results. The reason I bought many domains was so that whenever a person searches the web and they type "buy a house" my website could be a top search result., if my domain would be buyahouse.com (as an example)

I submitted my main website to google, also the domains to google in webmaster tools; however when I type that specific set of words my website or domain doesnt show in google. Only the if I type the main domain it will show. I might be doing something wrong, if so can you please explain or guide me on how I could use this other 20 domain names so that would help mu main weboste get visitors. Thank you in advance.