It lets you look for solutions to the opponents threats, as well as find your own key cards to win the game
Ezuri, Stalker of Spheres is a strong roleplayer in Proliferate decks, and could make for a fun Commander
You can then use this card to chump block and sacrifice it to go find a land, giving you a bit of extra time and mana
With that being said, here are some really good black board wipes MTG has printed that fall within that budget umbrella: 1
I had enough to swing 23 damage with my biggest creature getting blocked, so I swung lethal on Marchesa and passed the turn
8 Olaf, Friendly Snowman He Loves Warm Hugs The fun and silly sidekick of Frozen has an Amethyst card that may not look like a lot on the surface, but is a very helpful one to have in the early game