eBay, TCGPlayer, and Card Kingdom are excellent resources for finding rare MTG cards
Cards that are printed many times usually have many different art versions, so youre usually looking at a $0.50 to $1.00 difference
The best strategy to use is to have a tanky Pokemon like Chansey or Snorlax soak up damage at front while you build your nukes at the bench and firing them off when available
As for those two EARTH machines, well you can definitely use your Ancient Gears, but you can also use Meklord Army of Granel or even Meklord Emperor Granel
As a large amount of the deck relies on your opponent having damaged characters, you want to avoid banishing too many of them
So you pulled a $1,000 Umbreon VMAX Alternate Art Secret card from an Evolving Skies pack you purchased at the Pokemon Center or your local card shop