I've gotten a few in the past and only recently learned you're supposed to give them to the mage, but whenever I do he only gives me these shards that... honestly don't have much purpose outside of being used as combinations for tier 6 spells. I hear that SOMETIMES you can get tomes from the mage, but I haven't gotten one yet...

It's annoying yes but you can always sell the amulets if you don't wanna take the risk in turning them in.

it's really up to you! i believe the rough estimate is that the mage has around a ~12.5% chance to give a tome and the rest of the time he'll give the inexpensive shards you've been getting, so mage quests are always going to be a gamble of sorts. if you're after tomes for a battle pet, it's really just a question of if you would rather keep the sp from selling the amulets and guarantee getting a tome (selling 8 of them would generally give you the sp needed to purchase a tome, and ~12.5% is about a 1 in 8 chance of getting a tome) or if you feel like it's worth it to take the gamble on turning in amulets and potentially getting more than one tome from the mage (because he can give them out more frequently than that, it's just up to chance).

(anyone can feel free to correct me on my statistics or numbers here if i'm wrong, by the way!)

I always sell mine, usually at the end of the month. I am aware of what they're for, which is not my interest.

For the record I sold an entire year's worth in December, about 700, to buyers for CSC or sP. I did rake in several thousand CSC and tens of millions sP.

I sold any that I got for years until my pet finally reached a higher tier and now I use them. Although, I’m not a huge trainer or battler, but I just keep pecking away at training, because it does add up over the years. But it doesn’t make much sense to use them before your pet is trained up relatively high, because it doesn’t seem worth the gamble from a selling perspective.

Same way you buy things with sP via the trade center, there's an option for CSC just underneath :)

There's also an achievement for having all of the mage amulets in your wardrobe at one time.