I used to click on random gmail ads to scramble the algorithm, but then I thought that it would be pretty easy for a computer to figure out that I'm not actually clicking through to the site.
So I started clicking through to the site. But then I realized that probably the computer can figure out that I'm not actually purchasing any of the items that I'm clicking through to see.
So now I just buy random goods and services through gmail ads, so that they'll never be able to tell what I'm actually interested in buying.