The Sea Dragon. You can buy it from the crowns shop or get it as a drop from the bosses in the Trial of the Spheres dungeon in Celestia. It's a great first generation pet, and an excellent pet to hatch with when customizing a pet.
Enchanted Armament is the best overall for any school, in my opinion. It gives you 3 sharpen blade cards long before you can get them so makes a good base for custom pets of any type. It's also one of the three most common trained pets in the game, so it's pretty easy to find a hatch with talents you want.
Like Seethe Said, Enchanted Armament Is Probably One Of The Best In Terms Of First Gen Pets. However, If You're Looking For A Good Talent Combination For Pets, Then You Could Potentially Use Whatever Pet You Want. I Personally Would Use Enchanted Armament Or Rain Beetle (For The Same Reason That Seethe Said He Would) And The Rain Beetle Because You Can Get A Maximum of 4 Storm Beetle Cards Which Damages The Enemy AND Gives You a +25% Universal Blade. In MOST Situations, A Pet With Resist And Healing Spells Is Most Ideal, My Mega Rain Beetle Has MC Unicorn, Healing Current, Sprite, Fairy, And Spell Proof (9% Universal Resist) This Type Of Pet Offers Good Defense, And Lots Of Healing. However, Some People (Especially PvP Players) Will Drop Healing Spells And Try To Get Triple Damage And DOuble Resist Pets (One Universal Damage, And Two School Specific Damage Boosts, And Two Universal Defense Boots) It All Comes Down To Your Play Style Though, And It Takes A Long Time Of Experimenting, Hatching, Training, Etc. To Finally Find A Combination That Works Best! I Have A Multitude Of Pets With Good Stats That I Could Hatch With You If You're Looking For A Good Stats Pet, But If You Want A First Generation Pet, Go With Armament. :)
The Sea Dragon. You can buy it from the crowns shop or get it as a drop from the bosses in the Trial of the Spheres dungeon in Celestia. It's a great first generation pet, and an excellent pet to hatch with when customizing a pet.
It has also been reported found in treasure chests while fishing in Olde Town.