In early try to just farm and chillout and don´t flame. No one likes *******s. Try to chear your team up if they are doing bad and say what they must do better. Try to get muramana fast as possible and try to get bluebuff cause you will allways ned to have full mana so you can burst even harder with muramana. Teleport is important because you won´t have much sustain so teleport is best solution. Check the notes i wrote at the item build for more details.

Stay behind your team and poke, play like a caster (mage caitlyn if it makes sence).
Focus their adc or squichys. Because your ulti will deal around 1000 dmg or more to their adc.
Try to allways stay behind your team and play like a caster. Then you will deal

This build is slow but very fun to play. You will be surprised how much damage your ult will do. It works really good!!!