Here are some tips that you can use for PPC advertising:
If you have a national campaign divide it to regions. You can do just only states and have 50 campaigns targeting each states. Have the state names in your ad names! If you have energy you can go even lower to city levels. It will require lots of work but it might worth to target the areas where your most sales come from.
Don’t be afraid to create ad groups so you can target your ad copies better. Each ad copy’s title has to include the keyword to get higher CTR.
To get higher quality score and pay less for your ads do this: when you first set your campaign up, create very relevant ads, target well and bid high. If your ads and your landing pages relevant you will get higher click through rates, people will spend more time on your landing pages, which will result higher quality score. When you already have a high quality score you can bid much lower to appear ahead of your competition.
Use Keyword Insertion Tool. This will help to increase your click through rate drastically. You can use DKI anywhere in your advertisement, the title, the ad lines, the display URL. I advise for you to use it more than one time in one ad.
Have at least 4 ads running in the beginning, switch off the auto rotation and wait a week. Keep only the best performing one. You can test others again only keeping the best ones.