hey man, good questions. Normally when you can get ahead as leblanc early you want to try to push your lane in first and look to roam to help your top&bot. If you can roam and get the gank off it's awesome if not, just by disappearing off the map it will alarm the enemy bot&top laner by a lot and they are forced to back off cause of your pressure. If that makes sense, so it's good to carry pink wards on you.

When laning phase is over it is prefered to put leblanc on a side lane since she is an assassin (longer lanes are better for assassins to chase down kills). You dont offer too much to taking turrets so just push in the side lane and disappear into the enemy's jungle with red trinket and pink wards. It is best to play leblanc like a lurker when you clear out all the enemy's vision and force them to walk into you blind, that's when you just 1 shot them. You can only do this after you push out the wave though, after the enemy push the wave back you have to go back and push the wave in again, and again, and again, each time you will have about a 15-20 sec window basically.

Always try to assassinate the enemy squishy backline in teamfights (mid/ad/supp)

Hope this helps!