CTR will vary by produce and industry therefore, your CTR can really only be compared to that of other ads you are running within your industry if you want a true idea of how your ads are doing. Obviously Google prefers that your CTR be over 1% so you are doing well enough for Google not to delete your ad.
To make sure your CTR to ROI is optimized, make sure that your ad is relevant to the products found on your site. For example, if your ad mentions "low prices" make sure the user is taken to the page that shows them bargains etc. A "sales pitchy" ad is great to get users to click through but if they don't see what is being said in the ad, they are less likely to buy something. Try deep linking to specific pages of your website so users don't have as far to navigate for the product being search for.