There is no true concept of initiative in FES. Everything revolves around what’s convenient to the narrative, so you get to basically invent what happens and represent this as a challenge.
In general, every player should get a single action-oriented challenge that they can deal or take damage before turn order resets. If a player could potentially take damage but has already had a challenge, this generally means that success simply means you don’t take damage, rather than dealing it out in turn.
Sometimes, turns can get really complicated, so rather than taking an I-Go-You-Go approach step by step, discuss with all the players about how the turn would unfold in terms of who has to deal with which challenges. This gives you a chance to decide not only what is happening, but how your character acts throughout the situation, rather than simply being forced to take a ton of defensive rolls.
In the context of combat or other challenging encounters involving non-player characters, it may be confusing to choose who goes first, whether you or the enemy - but remember, the player makes all the rolls, and failure indicates success on behalf of your opponent, so realistically it’s more about figuring out which challenge each player is responsible for overcoming, rather than to deciding who goes first.
When navigating multiple challenge sources, consider the following:
- What are the groupings of engagements in the challenges? If you’re outnumbered, you should represent this by granting yourself disadvantage based on how you interpret the seriousness of being outnumbered, rather than dealing with multiple challenges from each enemy. If you’re facing two enemies in front of you, you may only suffer a single disadvantage, but if they are flanking you, they could even give you two disadvantage dice!
- How are the players working together? If one of the players fails, who would be the one to suffer the consequences? Generally speaking, this means that the person who would suffer should be the one to roll, with advantages granted by the other player’s acquisitions and effort. In a case like this, you should transfer your advantages and disadvantages to the character who would suffer, and if working together in this way makes sense to grant extra advantage, add that in!
- It’s possible that multiple players may need to engage a single challenge separately, such as dealing with a fireball blasting the entire party. In a case like this, each player needs to decide beforehand whether or not it makes sense for their character to be able to retaliate or not. If they can, then they can face that challenge directly. If they cannot, and would be making a separate challenge, you should consider turning the fireball into one or more disadvantage dice on that character’s challenge instead.
If you’re trying to run the game more traditionally, and want there to be a rigid turn order, that’s fine! Be warned that this typically will result in a more lethal game because you have to roll more since each challenge becomes a separate event, but if you want this experience, a good rule of thumb would be to consider the initiative its own challenge with no consequences other than deciding order based on how high over or under the challenge source’s DC each player rolls.