One of the best ways to identify which landing pages need improving is to use the data found in the keyword's Landing Page Experience quality score sub-factor.
Adalysis analyzes, weekly, all your landing pages that are used in the Ads Final URLs (the keyword Final URLs are not taken into account). It will alert you, in the dashboard (under Audit Alerts / Landing Pages) to any landing page which has more than half their impressions come from keywords with below average landing page experience.
Clicking on the above alert will open the Landing Pages screen showing you the ones that need improving:
To improve the Landing Page Experience factor for a landing page, you will need to improve the relevance of these keywords to the landing page. Carefully examine how each keyword with a below average LP experience relates to the content of the landing page.