Looking on the internet deeply has found these results:

a lot of effort is the most popular phrase on the web.

a lot of efforts 142,000 results on the web	a lot of effort 129,600,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Apr 3, 2014 ... I disagree. the difference between hard and hardly lies there! hard May 26, 2014 ... There have been a lot of efforts to protect and restore the Chesapeake Bay. Those efforts are noble. But they're not enough. It's beyond time to ... earned money A lot of efforts have been done all over the world to make sure that women are protected against all kinds of sexual harassment and discrimination at the ... you do a lot of efforts and earn money. hardly achieved ... kill two birds with one stone. exp. to do two things at the same time using the effort need... beat one's brain out. id. make a lot of efforts to understand something ...	It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

a lot of efforts

142,000 results on the web

a lot of effort

129,600,000 results on the web

More popular!

Apr 3, 2014 ... I disagree. the difference between hard and hardly lies there! hard
May 26, 2014 ... There have been a lot of efforts to protect and restore the Chesapeake Bay. Those efforts are noble. But they're not enough. It's beyond time to ...
earned money
A lot of efforts have been done all over the world to make sure that women are protected against all kinds of sexual harassment and discrimination at the ...
you do a lot of efforts and earn money. hardly achieved ...
kill two birds with one stone. exp. to do two things at the same time using the effort need... beat one's brain out. id. make a lot of efforts to understand something ...

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.