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.