50.What level of righteousness must one reach to receive the Holy Ghost?

A person can never be good enough to earn the Holy Ghost. It is a GIFT to the believer through the goodness of God[grace] and can be received suddenly, quickly, easily.

Isaiah 64:6
6. But we are all as an unclean thing, and all our righteousness are as filthy rags; and we all do fade as a leaf; and our iniquities, like the wind, have taken us away.

Ephesians 2:8
8. For by grace ye are saved through faith and that not of yourselves: it is the gift of God.
9. Not of works, lest any man should boast.