Abzan Advantage is a common Instant card from Fate Reforged (FRF), collector number 2. Current market price: $0.18 (foil $0.29), TCGplayer market prices via Scryfall.
Target player sacrifices an enchantment of their choice. Bolster 1. (Choose a creature with the least toughness among creatures you control and put a +1/+1 counter on it.)