The hard part for a designer is how much cool design space to give away to making money with Google Ads. Do most of you design your sites with no ads at first then ad them as you get traffic? On the flip side...sometimes adding a larger leaderboard and med rectangle image ad actually seems to add some visual credibility as most major sites have a similar look.
The best option would be to integrate ads into the design by matching colors and shapes. This way you get both - higher CTR from well placed ad blocks and beautiful design. Also there is no need to put a lot 1 link ad unit and 1 text ad unit is usually enough.
I put the ads on right from the outset, otherwise potentially you might have to redesign the site to accomodate the ads at a later date, thus making extra work for yourself. I have certain sites that even at only 5 - 10 uniques a day are steadily earning 50p - £1.00 a day, why throw that money a way.