Three damage is enough to deal with most early threats in Standard, and being able to use Vibrance like this avoids the issue of your five-mana creature languishing in your hand all game
Its unlikely that youll want to mulligan both of them, but it can happen
Dont sleep on it
Get a couple of creatures on the board and continue to pressure the opponent's life total whenever you can do so without risking one of your attackers
Know Your Nine The "Power Nine" refers to nine cards originally printed in Alpha: Black Lotus, Mox Sapphire, Mox Ruby, Mox Jet, Mox Emerald, Mox Pearl, Time Walk, Ancestral Recall, and Timetwister
Teferi, Hero of Dominaria A planeswalker from a time when control was king, Teferi, Hero of Dominaria has a bunch of really useful abilities