As kalista, Your r will hit like a truck and allow you to quickly take neutral objectives. Take all the objectives from the map and don't do anything which may have the chance of getting you killed.

Get a defensive item when possible. This should help a lot if you manage to mis-step during a major skirmish. Only go in when the enemy has used up all the primary forms of CC.

You will be a prime target for assassins, so make sure you are wary during fights. Also, use your W carefully to cover your flanks when you get the chance to do so. As kalista, Your r will hit like a truck and will allow you to quickly take neutral goals. Take all the goals of the map and do nothing that could have the chance to get you killed. Get a defensive element when possible. This should help a lot if you manage to take a bad step during a major skirmish. Enter only when the enemy has used all the primary forms of CC. You will be a prime target for the assassins, so make sure you are careful during the fighting. Also, use your W carefully to cover your flanks when you are lucky to do so.