First step - stop thinking about keyword ranking!
There's no need to worry about the ranking of words - that will come naturally. The days of focusing on a single keyword and doing blackhat to make it to the top of the list are long behind us.
As long as you're doing thing naturally, and regular phrases and wording is being used, you'll start to rank for words on their own. But even then, don't pay attention to the rank position - there's only two things you should be paying attention to;
1) Traffic coming to your site
2) Conversion of that traffic to paying customers
If you're getting traffic, and it's not converting - you have a problem. If you're not getting traffic, then just regular ole advertising and hard work in writing will get you the traffic you desire.
First step though is to make sure that all the traffic you're currently getting is actually converting. No point in advertising if you can't even close the sale to begin with.