When I actualy did rituals and dressed for them, I think I had about 5 different gowns.
Two had spaghetti straps and an empire waster made from rayon.
One was two pieces: a linen underdress with long bell sleeves, empire waist, scoop neck. The over dress had a deep shawl collar, sleeveless, buttoned to just under the bust, and was open down the center front. I wore this at Imbolc usually.
One was black velvet, v-neck, mid-calf lenth. 3/4 length sleeves with a flounce (think the sleeves from the Baroque period). This was for Samhain. Empire waist (i think all my dressed have an empire waist)
Another was peach linen, v neck, slightly off the shoulder, long sleeves with a ribbon running down the top so that you could pull the ribbon and tie it at the end, turning the long bell sleeves into gathered3/4 length sleeves. I *loved* that style of sleeve.
My last dress was red velvet with a gathered bodice, empire waist, short, cap sleeves. This was for Yule.
Oh yeah, one more.

This was a reversible dress--it was really cool. Sleeveless, empire waist, a-line skirt. The tops of the straps had eyelet holes which I laced together with ribbon (so the straps come undone at the tops of the shoulders). This gown was lavender linen on one side, and a pale blue cotton on the other side, fully reversible. It was a little heavy, but it was way cool.