Bloom Hulk is one of the best cards you could get for an Amass-based deck. It puts a 4/4 body on the battlefield, buffs your zombie token, and all that costs only four mana at common rarity. What's not to love?
Also, Proliferate ability doesn't limit itself to creatures or players, but it can also add loyalty counters to your planeswalkers, which are the main selling point of War of the Spark. So give it a go even if you don't run Amass tokens in your deck.