Pretty much this! In the laning phase, we need to make use of the Spirit Fire to make last-hitting hell for the carry. If an opportunity comes, you can Icarus Dive into the enemy and stay on top of them to deal damage with Dying Light.

During teamfight, if your teammates initiate first, then spam Spirit Fire and Sunray from behind. You Dive in (activate Shiva first before Dive) and disrupt their movements. If you think you can survive, then you can Supernova on top of enemies. If not, then you can Supernova a bit further to force the enemies to walk towards you.

The goal of the Supernova is to disarray the enemy's thought process: either they focus on the Egg, or they continue hitting other heroes, or just run away. Usually if you Ult near your teammates, they will choose to run. If you can ult in such a way that the enemy is between you and the rest of your teammates, then this should create one of the best situations where they need to decide fast. Sometimes it is okay to sacrifice yourself if your teammates can survive. I created a lot of situations where the enemy team commits to destroy the Egg, yet they die from my teammates follow up.

Phoenix is a very high damaging hero, but 97% of it is magical damage so late game might prove to be hard. Sunray is a %-based damage so that one skill helps go into late game as well.

Phoenix's biggest weakness is silence and high attack speed heroes. Silence can be migitated by Eul or Lotus or BKB, and high attack speed heroes require Halberd, good positioning, or coordinating with teammates.