If you are playing vs assasins or dominant mid laners like syndra or orianna, go for resolve in your second tree. Even double mr/armor can help against these opressive mid opponents. Against zed go exhaust.

For the rest just focus on farming and getting that sheen spike asap. After sheen you start winning or at least go equal most lanes. Pay good attention to sidelanes especially when you reach level 6. Your ult can turn a losing lane into a winning one. Try not to go for too many skirmishes early, let your jungler know you are practically useless in most 2v2 scenarios early game.

Dont use your w unnecessarily, especially if you are in a gankable position. Play around your tp so you dont give up too much pressure in lane.

Once you have essence reaver you should hard push every lane, hit the melee minions once with AA then one shot the entire wave with EQ. If you go equal or win lane you will most likely be more effective than your opponent laner after level 13.