Fickle Fortune is one of those cards that starts off interesting, and only gets better on analysis. At its very basics, Fickle Fortune is a 3 XP card that can either act as a powerful team-wide heal or doom removal - two very useful effects depending on exactly how your team is doing.
If you're choosing the first effect when you draw it, you're adding 1 doom in exchange for up to 6 healing per player. This is incredible action compression in some ways, since it is a rare player card that scales with player count, meaning it only becomes more impressive as you have more investigators. The downside is that it scales this way in exchange for doom, but the second half of Fickle Fortune will help you mitigate that. And, since it adds doom that doesn't advance the agenda, this can end up being free healing at the right time.
If you're choosing the second effect when you draw it, you're effectively removing 1 doom in exchange for some additional time. The damage isn't negligible, but it's also not too severe - it's what I would consider within the buffer of what most investigators try to keep to avoid going down to an unfortunate encounter card. This does remove Fickle Fortune from the game as well, so it shouldn't be picked if the healing portion will be necessary later.
Even before getting Survivor tricks involved, this is a powerful card that lets you choose if your team needs Healing or Doom more at any given moment. Neither of the choices involve costs, and the doom addition/direct damage means both options will always change the game state, so you can always pick the one that will help more or harm less. If you're going all the way and purchasing two copies, the net effect of both copies will still put you to a net of 2 health and 2 sanity per investigators for two cards and no actions - a reasonable exchange rate, even before getting extra value from it.
And, of course, survivor tricks like Resourceful and Shrine of the Moirai will only help to get this back in your hand hand at the exact moment where you can make the most use of it.
Of course, if you really have a lot of XP to spare, you could run this with Soul Sanctification in a 4 player game, draw this early, and grab enough offerings to last for a full scenario. Carolyn Fern and Vincent Lee get to throw a few more gifts around on top.