Rather than spend the extra time to determine a full initiative order and track it, I prefer to use the Popcorn Initiative rules crafted by The Angry GM. Simply put, the system works by everyone rolling initiative, and the person with the highest roll goes first. Once that person has gone, they choose another combatant to go and so on until everyone has gone. The last person to go chooses who will go first the next round.
When a PC fails a roll they receive one XP.
Whenever, the GM spends a destiny point to upgrade challenges for the players, one XP is added to a pool. This pool is then distributed among the PCs as the players see fit at the end of the session.
The Glow of Success
When a PC rolls a Triumph, they may choose to spend it for an XP instead of a standard spend.