XPOff

You have 300, want to farm 700, to buy something for 1k, so you don't lose the 300? Or am I wrong?

I would just spend the 300 and farm after the patch hits

Yes but the farm 500 charms achievement

I believe in you

I Like this spot: the Clackers on the northern tip of Highmountain
Use a tank spec and mount to round up groups without getting dazed/dismounted.
Kill them, roundup next group
Loot after all are killed, log out for 5 mins. to allow respawn

Avg of ~20 pet charms per login

Was more successful by killing all then looting all. I suspect some kind of cooldown mechaninc on the shoulder enchant.

The preferred zone is the Murlocs in Azshara, but thats a good spot too. It does indeed have a 1 hour timer CD, and the CD begins once you loot a bag.

The cd is not always the same, I've had times where I've looted bags within 15min and I've had times when I wasn't able to loot a bag for 2h, so I don't think it's an exact timer.
But the most important thing is that the cd is char specific, so if u got a bunch of alts you can go between alts to farm a lot of bags.

I think diff chars have diff drop rates too, like my monk's pet charm drop rate is like pulling my eye teeth out, but on my hunters they drop like candy (comparatively speaking) idk.

Edit: I concur with Conzil re: cd. I just got two bags off two separate loot piles within 8min of each other (on the same toon without logging out) so it's defo not 1hr.