Good luck!(Thank you.)
Good luck!(Thanks, I need it.)
Good luck!(You too.)
Good luck!(Good luck to you, too.)
Good luck!(Let's hope I don't need luck.)
A:I'm so nervous for tonight.
B:Good luck! You'll do fine. A: Thanks.
A:I heard you got engaged. B:Yes, we're getting married in June.
A:Congratulations! B: Thank you.
A:I graduated high school with honors!
B:Congratulations! I always knew you could do it. A:Thanks.
Good luck to you, too.
Thanks, I need luck.