I Googled a keyphrase for my campaign but I don’t see my ad—why?

Some potential reasons are you are in a competitive industry, you have other key phrases that have proven to convert, there's low search volume, and where you are searching (Google) from.

Why don't my ads appear at the top of the page when I search on Google?

A smart approach would be to work your way to the top by generating affordable leads in a short amount of time with a small amount of budget by bidding on lower position, higher quality keywords. Then start to scale.