In the early game you should play kind of passive. There are plenty of bad matchups. Ask your jungler for ganks or farm up. You wont do alot of damage early.

In the mid game you get your powerspike with trinityforce and deadmans blade. You will be pretty strong.

In the late game you are really strong. You can always jump into their backline and go away with your ultimate. You have alot of mobility and you are super tanky.

In the early game, you have to be aware of your mana, so dont use your Q too often for waveclearing. Later, you have enough mana and alot of waveclear with your Q.

You are an okay splitpusher, but after the first tower you should go and help your team in teamfights. But make sure that the enemy toplaner doesnt get your tower.