St. Clement, an eminent Christian philosopher and mentor of Origen, is known as a strong opponent of Gnosticism. He insisted that knowing God is not a matter of esoteric knowledge attained only by a few initiates with the right friends, incantations and crystals, but is available to all who seek God in relationship; that we are the ones who limit an intimate connection out of fear, selfishness and shame, while God stands ready to receive us and embrace us.
If you define Gnosis as you have here (“right friends, incantations, and crystals”) then, of course, Clement would be opposed to it. He proposed a Christian Gnosis, however.. His wanted to bridge the gap between Gnosticism and “orthodox” Christianity, but what you have said, “;;;available to all who seek God in relationship…” is a good definition of what he, himself, suggested was the true Gnosis. Of course, there was more to what he taught than this. Also, he was not afraid of borrowing language from Gnosticism. Actually, as you undoubtedly know, that in spite of traditional opposition to Gnosticism there was still an influence on Christianity (if you look for it).