Put the rest on the bottom of your library in a random order. While three or less might not sound like much, MTG is full to bursting with cards which only cost three mana or less that can win a game
Questing Beast 8 Surrak, the Hunt Caller 9 Garruk Unleashed 6 Garruk Wildspeaker 5 Shifting Ceratops 5 Gemrazer 5 Vengevine 4 The five drops continue to have hard hitting power and have far more playable cards than other slots
Many, many more Allies were revealed on August 12, in both the main set and the Commander precons
Put four +1/+1 counters on it
Herald of Hoofbeats brings back Horsemanship - which right now is like flying but better and Chivalric Alliance is a neat white card draw spell (gosh this colour is getting better at that)
Modern Horizons 3 contains the 5 basic lands (Plains, Island, Swamp, Mountain, and Forest) with variant treatments, plus an uncommon Snow-Covered Wastes (included as one of the 101 uncommons) with its variant treatments