As a Gardnerian (BTW), We don't do a lot in the area of spellwork, outside of healings, blessings and protection spells, for the most part. There are some that we do that are oathbound and part of oathbound rituals and because they are part of the tradition's BOS, so they will not get posted here.
However, the best spell that ANY witch, traditional or eclectic, can do would be the ones that we write ourselves as individuals.
Of the spells out there, that I have written, is the one to draw the person you are meant to be with to you. It brought my soulmate and HPS to me in a time when she was most needed to come into my life.