First thing I would do if money is an issue is make sure your keywords, keyword groups, content, URL, ad text etc is as relevant as possible meaning your quality score will increase and decrease your CPC.
Second make sure your keywords are correct
Third make sure your keywords are correct.
Personally I've alot of impression and low conversion I know my keywords or landing page is wrong.
I.E if you only sell cook books, make sure you optimise for cook books, and if a person clicks on your ad they are brought directly to the information they want.
Add a range of word types {negative, broad, exact etc} so your not getting invalid clicks due to people searching for things like phone book, kids book, school book, work book, book club, etc
Another avenue is to spread the rate at which your ads are shown if you only operate at certain hours you may want to increase the rate at which adds are shown during these hours {i.e. pizza delivery}
Hope this helps
