Rainbow's experience with wintergreen is typical; like many woodlanders it has very specific needs in soil biology and if the soils is not suitable it just curls up and goes...

If ajuga is frying wintergreen is almost sure to...
Good old
Vinca minor is evergreen and prolific and cheap. More sun than shade makes gingers a poor choice, but it's likely not enough sun for junipers or thyme... Bearberry or
Arctostaphylos uva-ursii might well work; I have seen it in dappled shade on the Cape, and it is a lovely groundcover, one of my favorites...
Buying a pot of this and that and experimenting for a year is a great way to test things and more than once I have been suprised by how something takes to a specific area...
HG