Test and tracking is the key to adwords..

Setup 3 ads with different words in the ad.
Adwords is all about testing which one will out perform the other.

Work on writing ads that the user would want to click on it. Now you don't want have clicks and no sales, so be careful. That is why it's important that your landing page works in hand with your adwords...

Example of 3 ads keywords to use:

1: How to ....
......


2: Instant download .....
.......

3: ....
Buy now $25.99....


Track and test which ads bring in the sales...once you got the top 1, create more ads trying to beat that one...

Here is tip: if you have one adwords that coverts great, use that same ad, and test it on other ppc sites.. and use that ads and test in with some ezines that offer ads in their newsletters...

Adwords is just one way of getting traffic and sales... There are many newsletters online that offer monthly ads for under $50... google and you will find