Prowess is a fairly weak ability (which isnt a bad thing, if anything, it makes it easy to develop and balance)
At that point you should just be playing things like Vapor Snag and Grip of the Roil
Infnite creatures - Urza's Factory + Voltaic Key + Rings of Brighthearth + Mycosynth Lattice + Infinite mana - Simply make a token with Urza's Factory use Voltaic Key, copying the ability with Rings of Brighthearth to untap both Voltaic Key and Urza's Factory , which is an artifact through the lattice, and repeat
For instance, when played with "Aragorn, Company Leader" from the MTG / Lord of the Rings collab, Tidus can move Aragorn's first strike, vigilance, deathtouch, or lifelink counter onto another card
Its primary card is The Black Cauldron, a three-Ink item that lets you move a character from your discard pile under the cauldron
Any of these makes an excellent first box