Taigam, Ojutai Master - helps you combo off and can provide card advantage if it sticks
Some stand out above the rest, whether by power, place in Magic: The Gathering history, or art
Whether thats an A+B combo like Sanguine Bond and Exquisite Blood, or a loop with Gravecrawler and Phyrexian Altar with a Blood Artist or similar in play, you should be comfortable in approaching the game in the way that your color pair is most comfortable
So, you equip your Elvish Mystic and swing
They allow you to cast spells that cost four or more mana from the top of your library
Goblin Engineer is a retro foil reprint, highly useful for artifact-based decks, and worth $9.48