Hi my name is warrogue and this is my guide to successfully win toplane with gentleman Gnar :)

Pros-
he is very mobile with his W
Good poke with his Q and W
When mega Gnar he can really change team fights with R
Good sustain

Cons
He can be really immobile when W is on CD when in Mega Gnar mode
in mini gnar form he can be vulnurable if caught off gaurd

You have to have really good communication with the team if you want to achieve good ulti's into Azir walls or Anivia walls. It is key to have good communication within the team.

Gnar is a very fun champion and very versatile and it is great to have his CC and poke ability within a team.