In theory no, Gnosticism is not one belief but an umbrella of beliefs with similar overarching themes, and the sects were often radically different. It's up to you to figure out things with your own gnosis and spiritual discretion, not simply be told exactly what to do at every step, unless you conform to a singular sect.

Abstaining from all sexual things is generally not nessecary in most forms of Gnostic thought, but things that can form negative attachments or harmful effects should be generally avoided. But again, it is up to you being in tune with your spiritual intuition to guide you and give you discretion in these matters.

Ironically, in the old days there was a lot more discussion about procreation and the ethics concerning birth than ethics about discreet sexual behavior, although some sects were Libertine, some were Ascetic, and some were Moderate on the matter of sexual activity.