if you're getting spam emails, it's because you gave some questionable websites your email address...STOP THAT! set up a second email to give businesses if they really need one. better yet, set up a new email for your PRIVATE use and use the old one for businesses, since it's already tainted.
but you don't have to SEE them if you use adblockers.
AdBlock Plus is my fave.
as for Google, they track everything you search. if you're logged in (which you likely are on an Android), clearing cache won't cut it. you need to log in to your Google Account to see and destroy your search history.
and you have to do that every time you want it cleared...