Its sorcery-speed for a reason at instant speed, itd be way too strong
Most decks can answer them in some form. This design philosophy becomes apparent on Barbflare Gremlin, a brand-new creature that appears in this deck, which combines the rules text from two older enchantments, Manabarbs and Mana Flare
Gideons Lawkeeper Magic has a variety of creatures you can pay a bit of mana into to tap creatures
Fodder Cannon references how rapidly goblins reproduce and how they view each other as expendable for the sake of war, especially if it means sacrificing an annoying cousin or two
Each plane card has a subtype, and thats its planar type
You can use Quagsires Wash Out Ability to move around any Water Energy, and its Hydro Pump attack can do big spurts of damage once you get enough Energy onto it