Where do you get that garnet side quest anyways? I had it for most of my first playthrough but never found enough garnet to complete the damn thing. Now on my second I've been saving garnet for that quest in advance and I'm overflowing with the stuff, but I can't find the quest, hah. Hope it isn't in Redcliffe. Redcliffe had some...issues.
it gives you money for it (i think 6 gold pieces) just keep them from the beginning of the game, I had 11 I think by the time I got the quest, in term of the quest you will need later on 15 poison extract, 12 love letters, 5 scrolls (bollinster or something can't remember the name) 10 garnet 10 health poultice, 10 mushrooms (the plants I mean) that's all I remember now, im sure there are some I don't remember
When life gives you bread, eat the crumbs as well.