Tweeting about your study group and spreading the word on the WS Ning site are great ways to get the word out. You should also post it on FB and any other social media sites you're on.
I did find the site redundant with the online coven group. Why should people join your site rather than that group, or why should they join both? Your site is very intensive, so its slow to load. A few less moving thing on it would be helpful. Are the moving waterfall calendar, world clock, and slide show really needed?
You should ask yourself what purpose things have before adding them. Will it further the goal of your group? The slideshow of Twilight actors doesn't seem to fit with your goal and is confusing to visitors. If you want to keep those photos it will help to have pictures of members of the group and Wiccan related photos added to them.
Hopefully, you will find some of my advice helpful. Good luck with your page.