With the charm you can buy in the new Dalaran :
- A toy : 1.000 charms
- 2 pets : 50 charms x2
- 2 pets : 100 charms x2
- 2 pets : 200 charms x2
=> 1.700 charms for the pets / toy.
You can still buy in your garrison or in the new Dalaran :
- 2 charms : stone +1 lvl of any families (a bag with random stones)
- 3 charms : stone +1 lvl neutral
- 5 charms : buff +25% xp during 1h
- 10 charms : buff +50% xp during 1h
- 15 charms : stone upgrade rare quality
and if you really need to, 5 charms => 25 bandages.
So yes, you should stockpile charms if you don't have anything to do, but :
- WoD rewards have been nerfed (-50% reward) and the garrison daily is now 1 per account instead of 1 per toon.
- Legion World Quest will reward charms and stones... etc
You should have done it before the nerf. I have stockpile a lot of charms / stones before the 7.0 went live.
(I used a few for a guildmate)