12 groups is good, but why not let people sort themselves into groups of similar personalities & needs, so their votes will be more relevant to others in the group.

If dividing by 12 would mean too few votes per group, make them overlap. So if your sign was (for example) Slytherins for Sunshine, your votes would affect 3 Slytherin signs & 4 Sunny signs (double for the combination), but not the other 6.