gnar

what do i do with this champ? i love him, i love playing him, and i have a decent win rate with him, but my god i feel useless every game. winning lane tends to be a challenge, and when teamfights start to happen, i dont tend to get many good situations to ult, then i go back to mini and we lose the fight cause i was a sitting duck. also, no keystone feels good on him. ive tried several different keystones and none of them felt good. i know gnar's not particularly great but i want to play him and get good at him. any tips?