Early game try to focus on last hitting as much as possible. Don't risk too much hp on one minion, try to get it with your Q instead. When you last hit try to hit your opponent while you are at it. This will help you to take down his pots and force him to go back. If you feel like you can bully him a bit more use your Q then E on him and when you are running away from him use your W to deal damage and get movementspeed or use the movementspeed to chase him.

Mid game you want to look for opportunities to make a gank. Check if they are low and are pushing the lane. But when you go in wait for example bot lane to go in first otherwise you will be locked down and you wont be able to do anything and they will get away safely.

Late game you do NOT want to go in first. You want to go in when the fight has started when they have used their cc on someone else. This will make it easier to survive and to channel your ult fully. If you get a kill or an assist during the fight and someone is low while you are using your ult you should stop ulting and do your Q E W combo and take the kill and then continue to the next one that you can take down that is low or low enough for you to kill.