Selenite promotes clarity, joy, and higher realm connection. It will be perfect. You can get in tune with a Selenite Guided Meditation.
It’s a strong crystal but fragile at the same time. I recommend you don’t get it wet!
If you’re seeking guidance from Freya, you can use a prayer along with an offering like the ones you mention.
Also, try searching and find what her epithets are (her sacred titles). If it’s a prayer you wrote yourself, it might be better. But you can use this one as inspiration or to get started:
Hail Freyja, Vanadis,
I ask for protection,
Under your falcon wings
And war-maiden’s shield.
Help me to make peace among my enemies.
Give me the courage to fight again
For if I am battle-slain in truth
May my actions be worthy of your choosing.
Hail Freyja, Lady of Sessrúmnir
Help me to set boundaries for myself
So I can honor the boundaries of others,
For as your home, when locked,
Is protected by your will
Let me be also protected
And closed against trespasses,
Yet may my hospitality be true
And help me act in frith.
Help me to pay fairly
And to accept fairly what is my due.
Show me your just ways.
Holder of Magic and Keeper of Mysteries.
Teach me to see the magic in all things.
Help me to move between the veil,
Allow me to walk among the worlds.
May I glimpse in your forge of dreams
By Seidhr rune-wise and true as words from your tongue.
Hail Goddess of Beauty,
Amber-laden Creatrix, Mistress of Brisingamen.
Ignite within me the creative spark.
Help me to bring beauty
Into my own deeds and all that I make.
May the fierceness of your eyes
Lend me their keen awareness
That I might see none other
Than your face before my work
Let me be ignited with Need-Fire, your Will.