Having constant access to cheap rummage effects lets you get a ton of value out of cards like Monument to Endurance and Surly Badgersaur
Best Izzet Mana Ramp Cards (Galazeth Prismari, Prismari Command, Storm the Vault) Izzet doesnt have a lot of mana ramp options, and while there are some that have niche appeal like Dalakos, Crafter of Wonders, the best cards with universal appeal lean on the acceleration provided by Treasure tokens to fix and generate mana
This doesnt have to be a combo more often than not its just a direction if the cards in your deck all point in the same direction that is to say all work to achieve the same goal, whether thats stockpile and use energy, mill them, give you a bunch of tokens and swarm or Craterhoof them or any number of ways to win, the deck is more effective than a jack of all trades, master of none approach and that was a seriously long run-on sentence, I apologize
The Wise Mothman Infinitely flickering The Wise Mothman enables an alternative wincon since your opponents will mill out and it provides an interesting intersection of mill and combat damage to let decks pursue two win conditions
Those five two-color pairs were neither all ally colors nor all enemy colors but rather a mix