Tiny Box of Tiny Rocks
From Many Boxes, Many Rockses. Please read: This was my approach that worked for me. I shared the results from only two weeks worth with a set of 13 characters.
The Tiny Box of Tiny Rocks is a toy earned from the Dragonflight achievement Many Boxes, Many Rockses, which requires using 
A Box of Rocks 50 times.
Guide awaiting review
Farm A Box of Rocks
A Box of Rocks is most commonly found inside the Zskera Vaults, and less often on the Waking Shores. Placement within the Zskera Vaults appears random across all tiers, including rooms that do not have a brown dirt cloud animation at the base of their doors. Zskera Vault Keys are purchasable with Dragon Isles Supplies.
Use Boxes on Alts
The Many Boxes, Many Rockses achievement is account-wide, so A Box of Rocks can be mailed to alternate characters and each use will count toward the 50 total. Note that there is a mail recipient limitation of 20 per send.
Buy from Auction House
A Box of Rocks is tradeable and can be purchased from other players on the Auction House if you need to supplement your supply.
