Everyone has to give his best in the first go
Say "his or her," "her or his," or rephrase. For instance:
-We all have to give our best the first go.
-People need give their best the first go.
-It's important to give your best the first go.
Diane Hacker, in A Writer's Reference, which was the university-wide reference where I tutored writing, says: "At one time he was used to mean "he or she." Today such usage is inappropriate."
I don't like 'in' either, should be 'on'.