Struggle to Survive

Whenever a creature enters the battlefield under your control, you may pay {g}{g}. If you do, put a number of +1/+1 counters on that creature equal to the number of creatures your opponents control.
{x}{g}: Reveal the top card of your library. If it has converted mana cost X or less, you may play it without paying its mana cost. Otherwise, each opponent creates a 1/1 green Dinosaur creature token.