You do realize that while there is an occasional use of the word gnostic to denote those who have true knowledge of God, the predominant use of the word, particularly with a capital G in English, denotes the broad species of early heresies which claimed “secret knowledge” of the divine beyond (and often contrary to) the Church’s publicly proclaimed Faith. (And this is so early that there was only one identifiable Church, still undergoing persecution by the pagan Roman authorities.)
Gnostic sects generally fell into one of two opposite attitudes toward sex — either they were libertines, regarding the use or abuse of the body as having no consequence for the soul, or they were rigid and extreme ascetics because the body was worthless and to be discarded — neither variety accepted the reality of the Resurrection, and both varieties regarded the Holy Apostle Paul’s dictum that the body is the temple of the Holy Spirit as folly.
I know little of Roman Catholicism except what history teaches. And their brutal history doesn’t reflect on them very well.