Yeah, it's tough finding the balance between 'my ads aren't showing' and 'I sold lots... oh and paid out even more.' I have to admit, my strategy of getting ads to run (high bids, but a lower budget so they didn't go crazy), and then paring them back a bit, does seem to be working.
One thing that helped enormously was adding the ability to import AMS reports into SalesScanner (my kind of homebrew Bookreport thing.)
I can see the breakdown of ad spend by title, across 4 markets, either daily, for this week or for the last 30 days, and whether I'm over-spending on one particular series. (Wouldn't be useful if you're running ads for 1 or 2 books, but I run them on 8 titles/series.)