I always think that it is good to wish people good luck, but no. Why not? Because if people got well prepared, they’re sure to make it. You should say, You can make it rather than Good luck. Good luck means you achieve something by chance, you’re a black horse, not everyone like this. People have skills are not succeed by chance, the make it by hard working, by actual strength.
If you believe someone’s gonna make it or try to encourage him, say You can make it!