fuindordm
Adventurer
Faerie Fire is an excellent spell! Not only does it give you advantage, it negates one of the most common sources of disadvantage first. There aren't many spells that can transform a disadvantaged attack into an advantaged attack, instead of disadvantaged to normal.
If you're fighting an invisible opponent, the math changes. Otherwise the math is the same as in the first post because you're comparing two scenarios with the same cost (2 spell slots for FF, then spell or spell, then spell). Casting FF is worth it if you would otherwise have disadvantage and need an 11 or better to hit, when it's just you in the combat. If you have a bunch of friends along, then you're boosting their expected damage as well. I dare say it is nearly always worth it, but there are too many variables to derive a general statement like I did before.
If you're fighting an invisible opponent, the math changes. Otherwise the math is the same as in the first post because you're comparing two scenarios with the same cost (2 spell slots for FF, then spell or spell, then spell). Casting FF is worth it if you would otherwise have disadvantage and need an 11 or better to hit, when it's just you in the combat. If you have a bunch of friends along, then you're boosting their expected damage as well. I dare say it is nearly always worth it, but there are too many variables to derive a general statement like I did before.