Placing wards in the very early game comes with its pros and cons. Warding too early is pretty much useless, but warding too late or not at all can get you killed.
Some champions like Twitch, Jarvan, Elise, Lee Sin, Shaco, etc., can gank a lane at level 2. Usually, this lane will be the mid-lane, but it’s not uncommon for them to gank the bottom lane.
If the enemy is one of these Junglers, try and place a ward inside their jungle in the early game to spot them before they make their way to the mid-lane.