Interesting idea, and potentially very useful... however, it seems to favor the Wiccan belief system. What if you spellcast by other traditions? (For example, karma is not acknowledged by all magical backgrounds.)
I know a lot of spellcasters use some kind of tarot spread to determine the efficiency of any potential spells; in fact it's been suggested to me that with such a high failure rate in spellcasting as I have, that I do divinations first to determine if they will be worthwhile, yet I've never found a good divination method for that purpose.
Also, I wonder about a spread for determining who, if anyone, put a spell on you? A lot of rootworkers in the old days are said to have been able to read playing cards to tell them who cast a spell and how they did it.
Just guessing kind of wildly at such a spread -- maybe someone can test it -- would be a three card spread.
1-2-3
The first card would be "Who cast the spell?" and only if it turns up a King or Queen would one proceed, since only their appearance would indicate a person had been casting spells. Whether king or queen indicates the gender of the person who put down the work. (I incline to use the Pages and Knights as well, except they would seem to skew the bias towards a male as having set the work.) Then, next card is "Why did they cast it?" This could be determined almost as much by the suite as the particular card -- wands would indicate revenge or quarreling, cups love, and so on, or I ought to think. The final card would indicate how best to proceed.
Alas, I don't know how to make a card say exactly where a trick was laid or what it was!