A 3-mana 3/3 with Vigilance is a great place to start, and doing dungeon stuff every time he ETBs OR Attacks is incredibly good, and that would be true even if he didnt also give you a massive bonus for completing the dungeon
Keep playing your deck, discover what you like best about it, and become the best player you know
So, you can have one copy of Thalia, Guardian of Thraben on the battlefield, but you cannot have two copies of Thalia, Guardian of Thraben
And to do this, not only does have good champions, good Commanders , not only do they have enough ways to make their creatures bigger and more viable, they also have the most ability to recur these Auras and Artifacts