I'll help you for that little I know.
Most of the present day "Scottish charms" are a relatively recent invention: they became popular during the early years of Queen Victoria's reign when everything Scottish became fashionable, the ones made using "Scots pebbles" (agates) particulary. The recent craze in Celtic designs did the rest.
Traditionally Scottish talismans and amulets took the form of brooches. The best known one is the brooch of Lorne: it was lost by Robert the Bruce at the battle of Dail Righ, became the property of the Campbells and later ended up in possession of the Macdougals of Dunollie, who still possess it (though many believe it to be a later reproduction of the original, lost in a fire). Sir Walter Scott wote about it in the Lord of the Isles. It was assumed to cure sickness and protect the wearer in battle.
A very popular talisman in years past (XVIII century on) was the so-called Luckenbooth brooch, sold as a "souvenir" at the High Kirk of St Giles in Edinburgh. Imitators soon sprung up in all of Scotland. It's still a pretty popular sight in jewelry and souvenir shops and its meaning is pretty obvious.
I'll post more as I recollect memories.