From least valuable to most valuable
10. Flawless Undead Battle-Stone
-> there are barely any cageable or old undead pets.. after 2-3 of those stones you are set. Senjin Fetish, Creepy Crate and Ghostly Skull is pretty much all you can use or buy those stones for.
9. Flawless Elemental Battle-Stone
-> Same reason as for the Undead. Theres barely any elemental pets you can use those on: Tiny Snowman, Ammen Vale Lashling, Spirit of Summer, Teldrassil Sproutling, Withers. After those 5 you pretty much have no further use for them.
8. Flawless Critter Battle-Stone
-> While there is a ton of Critters to use Stones on you will also need a ton of those. The good news is that they drop often.. for example making genocide at valley of four winds nets you quite a lot critter stones. Pets to upgrade: Scooter the Snail, Armadillo Pup, Perky Pug, Mulgore Hatchling, Elwynn Lamb, Spring Rabbit, Silver Pig, Golden Pig, Pint-Sized Pink Pachyde, Peanut, Egbert, Wolpertinger, Brown Rabbit, Whiskers the Rat, Mr. Wiggles, Winter Reindeer, Snowshoe Rabbit, Brown Prairie Dog, Undercity Cockroach, Singing Cricket, Imperial Silkworm.
7. Flawless Beast Battle-Stone
-> Similar to Critters, Beasts are the most dominant pet type out there, so there will be plenty of opportunity to get those. Pets to upgrade: Bombay Cat, Cornish Rex Cat, Black Tabby Cat, Orange Tabby Cat, Siamese Cat, Silver Tabby Cat, White Kitten, Albino Snake, Black Kingsnake, Brown Snake, Crimson Snake, Worg Pup, Smolderweb Hatchling, Poley, Cobra Hatchling, Baby Blizzard Bear, Dun Morogh Cub, Durotar Scorpion, Calico Cat, Darting Hatchling, Deviate Hatchling, Gundrak Hatchling, Leaping Hatchling, Obsidian Hatchling, Ravasaur Hatchling, Razormaw Hatchling, Razzashi Hatchling, Winterspring Cub, Feline Familiar
6. Flawless Aquatic Battle-Stone
-> They are not so hard to farm, but harder than critters and beasts. You can upgrade the following pets: Wood Frog, Tree Frog, Jubling, Speedy, Mr. Chilly, Sea Pony, Shore Crawler, Tiny Goldfish, Fishy and if you are unlucky with Wanderer's Festival Hatchling... the Wanderer's Festival Hatchling.
5. Flawless Flying Battle-Stone
-> Flying stones not soo easy t o come by.. not a lot flying pets to farm
them but a ton you need to upgrade. Following pets can be upgraded: Cockatiel, Green Wing Macaw, Senegal, Ancona Chicken, Hawk Owl, Great Horned Owl, Westfall Chicken, Blue Moth, Red Moth, Yellow Moth, White Moth, Miniwing, Tickbird Hatchling, White Tickbird Hatchling, Plump Turkey, Tirisfal Batling, Blue Mini Jouster, Gold Mini Jouster, Rustberg Gull, Tiny Flamefly, Gilnean Raven, Jade Crane Chick, Imperial Moth,
4. Flawless Mechanical Battle-Stone
-> Theres not a lot mechanicals to upgrade but also not a lot to farm (Winterspring). Pets to upgrade: Mechanical Squirrel, Pet Bombling, Lil' Smoky, Lifelike Toad, Tranquil Mechanical Yeti, Clockwork Rocket Bot, Mechanopeep, Blue Clockwork Rocket Bot, Personal World Destroyer, De-Weaponized Mechanical Companion, Mechanical Pandaren Dragonling
3. Flawless Dragonkin Battle-Stone
-> Not a lot high level places to farm Dragonkin stones (Borean Thundra) and usually overcamped. Theres quite a bunch pets to upgrade: Thundering Serpent Hatchling, Tiny Red Dragon, Tiny Green Dragon, Proto-Drake Whelp, Essence of Competition, Blue Dragonhawk Hatchling, Silver Dragonhawk Hatchling, Red Dragonhawk Hatchling, Golden Dragonhawk Hatchling,
2. Flawless Humanoid Battle-Stone
-> Since there are barely any Humanoid pets at high levels (Kun-Lai Runt) you wont see them often except for tamer dailies. Very rare and theres quite a few pets to use them on: Curious Oracle Hatchling, Curious Wolvar Pup, Peddlefeet, Gurky, Winter's Little Helper, Father Winter's Helper.
1. Flawless Magic Battle-Stone
-> Theres quite a lot magic pets to upgrade: Willy, Enchanted Broom, Jade Tiger, Onyx Panther, Zipao Tiger, Toxic Wasteling, Enchanted Lantern, Magic Lamp, Legs, Lunar Lantern, Festival Lantern, Jade Owl and of course if your unlucky on Minfernal .... well... Minfernal, The Magic stones are hard to farm making them the most desireable of them all