I would focus more on the conversion rate of sales/ROI. You can have a high CTR while still having poor sales/conversions. Also depending on the price point of your product/service, a low CTR and conversion could be ok. Like if your product was $1k or more and only took $100-$200 for one conversion/sale-positive ROI.
An advertising campaign should not be set and forget. You should always try to improve. Do so on both sides: the campaign and your landing page. CTR is a relative measure highly dependent on ad position and a few other factors. That's why there's QS to give you an idea of how you compare to competitors. The idea is to advertise so I tell clients put as much money as is needed to reach all searches or as much as you're willing to spend if that amount is scary. But as kjh said, typically you want to make sales, so if your landing page hasn't done that, you're just spending more without returns. Stop focusing on CTR or CPC. Optimize your campaign for ROI.
first of all you should check campaign that you are create. then check your keyword competition which keyword is more clickable.. then decide what cost you want... increase your quality score..