Do you use your homepage as a landing page or make a separate landing page targeted to each search term? Does Google ranking affect quality score? Will this impacted our Adwords Charges too? Anyone has any idea?
On Google adwords you get a quality score along with a bid. Just because your Homepage ranks for Red Widgets does not mean example.com/blue-widgets ranks for Red Widgets which means the homepage will only have a high quality score and conversion if it is related to the keywords you are targeting. If your Homepage is about Red Widgets then you may use your homepage as the landing page. When creating campaigns or doing Onpage SEO it is important to think of each part of your website as it's own website. It needs correct hierarchy as well as keywords. Focus on a handful of keywords, setup your campaign and your quality score/conversions should reflect how well you matched up the keywords to inner pages.
if you want to make a good landing page, try more usefull for your visitors. it's simple, if your site full of information, then you can get a good quality score.