You should sell Philosopher´s Stone and Heart of Gold if your inventory is full to exchange them with better items.

If you want to Jungle leave Philosopher´s Stone and Heart of Gold out and buy Doran´s Shield instead.

Use smite for jungling.

Try to gank as often as possible at the beginning. But make sure that you have skilled your Q, W and E

In Teamfights: Pick a squishy with your Q, activate your ultimate, slow the enemies around you with your E and kill the squishy with your W.