Devotion to the feminine Aeons
Half of the Valentinian pleromatic community of beings is feminine, and there is absolutely no reason why a modern Gnostic should focus solely on Christos and Sophia. We have Silence/Grace, Life, Pleasure, Love, and others - the many feminine aeons are worthy objects of devotion, remembrance, and contemplation. They all embody and represent eternal principles of Good Things, and by approaching them in a kind of I-Thou relationship, you're building your own relationship to those Good Things and to the Fullness as perceived by our historical Gnostic predecessors. That plurality and richness of the aeons is a beautiful theological achievement of Gnosticism - we are enmeshed in that plurality and richness, and so remembering our divine origin and remembering the unmitigated goodness of the Father involves also remembering our "aeonic family above."
How would one go about doing that in practice? You can write devotional poetry for them and prayers addressed to them, you can contemplate them using whatever contemplative prayer method you like (I very much recommend the Centering Prayer with a focus on the names of the feminine aeons), you can compose a liturgy/ritual to show your love and reverence towards them and towards what they represent, you can create artistic representations of them. All of these "worship modalities" are precedented in historical Gnostic practice, and an authentic way to tap into that ancient Gnostic creativity in building a relationship to the Fullness. For reference, have a look at Irenaeus' description of Marcosian rituals - they invoke Silence/Grace and the Higher Sophia, and so serve as good basis for any new prayers to other aeons.
I'll leave actually qualified people to comment on Sethian aeonology, but I think the same principle stands there too (even as it is a lot more creative in terms of the theology of gender than the Valentinian tradition). Likewise, feminine divine figures are also very much present in Jeuian and Manichaean traditions (the Xiapu Ritual Manual of Chinese Manichaeanism also contains prayers to feminine aeonic figures), and one of my favorites is a lovely hymn to the Daughter of Light in the Acts of Thomas.
Remembrance of Gnostic heroines
Mary Magdalene, Salome, Helen, Marcellina, the unnamed women involved in Marcosian communities, the women who helped with Paul's mission, Cathar women leaders, the Sophias (female bishops) of the French Gnostic Revival - some of them are more legendary than historical, but the historical Gnostic women who led and taught our traditions are incredibly important as human beings who made this Gnosticism thing live and survive and return. Some of them can be commemorated on days when they are remembered by various Christian Churches, all can be commemorated whenever you want to do so. You can always send a prayer to the Father and Mother in thanks for the illumination that came to us through Gnostic women.
The feminine Holy Spirit
1st century Christian literature made important mentions of "the Spirit", but 2nd century theology (both Gnostic and Orthodox) was still very fluid about who/what this Spirit was. Importantly for our purposes here, it seems that some Gnostics (along with other early Christians) understood the Holy Spirit to be feminine divine being, and possibly the Divine Mother of Jesus/Christ.
The femininity of the Holy Spirit is expressed (or hinted at) in the Gospel of Philip, the Gospel of the Hebrews, the potentially Syriac-derived Marcosian ritual formulas, the Gospel of Thomas, extremely strongly in the Gnostic poetic sections of the Acts of Thomas - if the Holy Spirit has a place in your form of Gnosticism, then there is a strong tradition of considering Her to be a feminine divine being, and you can continue that tradition whenever you call upon Her as Her. For reference, the poetic invocations of the Spirit for baptism and for eucharist as recorded in the Acts of Thomas are a wonderful (and immediately "prayable") example of how Gnostic devotion to the Spirit may sound like; as can the glorifications of the Spirit in the Gnostic sections of the Acts of John.
Thunder Perfect Mind
Most people have an appreciation for this text as a mysterious and immensely beautiful example of Gnostic thought, but for the practicing Gnostic, it can be quite a lot more: a call. The speaker is a mysterious feminine divine figure - is she Zoe, Sophia, Eve, Helen, all of them? What does she ask of us to contemplate? What does she call us to? When you consider these questions and engage with the text as a genuine record of an experience of this complex feminine divine being, and of the deep spiritual insight She wants you to gain, when you consider it a call to you today - then this is a kind of initiation through reading (Lesemysterium as some German historical theologians call this phenomenon) directly at the hand of the Divine Feminine.
...so by way of conclusion
When as newcomers we thought of Gnostic theology, who did we "see" (that is, who and what populated our imagination as we were reading and contemplating)? Chances are, our imaginations were often dominated by the Demiurge, by the archons, maybe a bit of Seth and Jesus, the fallen Sophia, a couple of 2nd century dudes. But I think that if we go beyond this "first impression" of Gnosticism, we can start noticing Silence/Charis the Divine Mother, Pleasure and Hope our aeonic sisters, the feminine Holy Spirit, the many Gnostic women who made a mark on these spiritual traditions - in other words, the presence of Divine Feminine figures, some theologically rich and complex and some evocative in directness and simplicity. And when we notice them - we can remember them, contemplate them, pray to them, pray in thanks for them, make them crucial parts of our Gnostic life (including in ways that don't need to be any more complicated than what our historical predecessors were doing).