Higher Quality Score (QS) affects on the each keyword bidding price to get higher rank position.
If lower QS, a keyword will be requested more expensive Minimum CPC and if both are lower it will be shown at a lower ad ranking postion.

Search Network Ad Rank = CPC bid price × Quality Score

The SQ for Ad Rank on Google and the search network is decided by those factors:

•The past clickthrough rate (CTR) of the keyword

•An account history, which is measured by the CTR of all the ads and keywords in the account

•The CTR history of the Display URLs in the ad group.

•The relevance of the keyword to the ads in its ad group.
*if you find many similar keywords in one ad group, it should be categorized and separated, and then make new ad group as a same type of keyword ad group.
•The relevance of the keyword and the matched ad to the search query.

•An account's performance in the local targeted area where the ad will be shown
•E.t.c