Google is now a corporation that answers only to its stockholders. This means that it is now exclusively profit-motivated. Private webmasters like you, me and your client do not bring a profit, but large corporations (what Google euphemistically is calling a 'brand') do bring a profit. Therefore Google is doing everything it can to prevent website owners from being able further their interests in the search results and giving that traffic to large companies that it can further profit from.
This is most obvious with commercial keywords. For example, if you do a search for sundresses, you will see large corporations that neither need nor deserve to be ranked for keywords. If a customer wants a sundress from Victoria's Secret, they will go to the Victoria's Secret site; Victoria's Secret does not need to appear for the keyword 'sundresses' too.
As you are finding out, the deck is stacked against you. You can have a great site with original quality content, clear navigation, and do everything right and it will not make a bit of difference. This is not the way it should be, and hopefully it will come back to burn Google later.
My long term advice is two fold.
Optimize for Bing/Yahoo first and for the time being forget about Google. You can make a good website and have it ranked well. Do no grey or black hat work. Over the long term I have faith that the public is going to get sick of the junk search results in Google and switch over.
Then start working on social media. Remember when I said that Google is taking away control over what you can do directly? It is ranking you by what other people say about you, so if you can get others to talk about your client's site, your client's site will begin to achieve Google search ranking. Go see hootsuite.com