Lucky. It's an older phrase so we don't really use it. We would just say lucky. So your sentence would say "May God bless you always and give you good luck."

This is a colloquialism that means one is lucky (but there is a nuance to it). "You are in luck..." is something a common saying when something fortuitous, yet perhaps unexpected, has happened. For instance if you go to the store looking for something and there is only one left of that item it would be appropriate to say "I am in luck!" However, if someone won the lottery you would not say to them "you are in luck" rather you would say "you are lucky". I hope that is somewhat clear!