Student or Learner
I think it is "our effort", but I am not sure.
We need context.
"Invading armies have no rights." Noam Chomsky
We are dedicating our time and effor/s to ensure that our customers.....................
We are dedicating our time and effort to ensure that our customers are happy.
Ok. But why nor our "efforts"?
You are speaking in general terms. You might use "efforts" this way: "Our efforts were in vain." (You made several tries, but they didn't work.)