Red will be able to use spells that deal damage to destroy things, and Green is stuff with cards that let your creatures fight other creatures
Ratchet does tend to offer better utility but Keg can hit some annoying lands and that is something not many cards do at all well
I have opted for some slower, permanent sources of spell doubling
9 Corpse Knight Corpse Knight is one of only a few Zombie creatures that requires white mana, meaning it's also effective in non-Zombie tribal builds, such as a dedicated Knights deck or any white-black go-wide deck
3 Tinker Bell - Giant Fairy When Tinker Bell gets mad, she gets big
You can grab removal dragons, token/value dragons like Miirym or Lathliss , or pure damage finishers whatever fits the board