And since 40 for a Noble Hierarch is clearly overpriced for what the card actually does, Id say Birds of Paradise is the best modern mana ramp creature right now
However, cards from older sets, rare Commander staples, powerful lands, mythic rares, foils, Secret Lair cards, serialized cards, and Reserved List cards can be worth checking properly
As the gentleman who helped me at the game shop that day put it after I explained, "You could not have picked a worse time to try and get back into this." And he's not wrong -- prices on some of the cards I would need to seek out like Charizard, Mewtwo and others, are already expensive now, and this is a project that will take years, not months, to complete these sets
Saruman, the White Hand 8
Its fantastically simple to set up infinite loops with cards like Banishing Knack or Retraction Helix to infinitely bounce 0-cost artifacts alongside Mirran Spy or other creatures that untap themselves when you cast an artifact