[Regret] "I'm not doing this for strength, but for what I believe in. And that's good enough for me."
[Phantom] ...A monster of ash and dust, its hands stained crimson, eyes of pale gold glowing softly in the dark.
These are the answers we've given so far. So I'm going to go through the options and pick the one I feel most appropriate given how we've already built Agnes up thus far.
[][Tail] "...Want the world to be safe and good and clean. For everyone."
This answer, this dream, I can see simply due to the fact that Agnes's choice of cleaning magic initially can be said to stem from her Phantom, and that her beliefs have been shaped through the good times and bad since then learning and expanding on her knowledge of that magic. She wants the world to be safe and good and clean, because she was scarred by a time when it was none of those things. When it was dangerous and bad and stained in blood. It's a pure dream, an ideal, and it is beautiful and tragic for those reasons. A solid choice.
[][Tail] "...Want everything to be happy. Like before."
This, this is the voice of a young girl who has lost everything that made her childhood good, has lost that innocence of youth, and it fits well with the Phantom. But it doesn't match up so well with her Regret choice, her statement of following her path for what she believes in regardless of strength. It's a desire, not a goal, at least that's how it feels to me.
[][Tail] "...Want to prove that my magic isn't weak."
While this could work, I feel it isn't Agnes. It also, as with the above, doesn't quite match up with the Regret answer. It's about strength, and Agnes has already stated she cares more for her beliefs than strength.
[][Tail] "...Want to reach the end of my path. Wherever that may be."
This is a good one on the surface, but it is very vague. What path is she talking about? Cleaning Magic? Personal growth? Life? Her wandering after leaving her home country? There's no clear goal here, and no way to really say how it fits with the other two answers.
[][Tail] "...Want to find a reason to live. To stay living."
This, this works with both in a very sad way. It states that Agnes doesn't have a reason to live right now. That even her pursuit of Cleaning Magic isn't a reason to live. That her Phantom haunts her this deeply. Agnes is just going through the motions, not truly living, but unwilling to just lay down and die for reasons she maybe can't understand. So she pursues her beliefs, hoping they'll give her something to hold onto, having already gained the wisdom to know that strength will not help her here. This one is more about personal, emotional growth. It would fit best with Phantom Lord, I think, as as a match between guild and dream.
[][Tail] "...Want to make people's days brighter, wherever I go!"
This is my write in option. I'm not...too sure of it, in comparison to Reason to Live and Good, Safe, Clean...but it's a goal that's both lifelong, achievable, and difficult. It involves both becoming better at magic and at social - Agnes wants to leave smiles in her wake wherever she goes. I feel like this is a beautiful goal, one that would help her battle her Phantom, and suit her beliefs. However this could simply be seen as another version of Good, Safe, Clean - it's simply that this option prioritizes happiness, which does not necessarily fall under the other option. Bit pedantic of me, I suppose, but I felt the need to put it out there.
[][Guild] "...I want to join Mermaid Heel."
This is, I feel, a limiting and yet freeing option. There isn't much mandatory interaction with the canon plot until several years down the line but we are free to pursue what we want to when we want to without worrying about that until then.
[][Guild] "...I want to join Phantom Lord."
This would be fascinating to explore. To see the man Jose was before he lost to his Phantom, and perhaps maybe even prevent the war with Fairy Tail entirely. But beyond that I'm not sure what this really offers that the other two options don't, other than perhaps combining a lot of what Mermaid Heel offers in terms of initial freedom with the option to join Fairy Tail down the road if the war happens.
[][Guild] "...I want to join Fairy Tail."
The hype choice. We dive headfirst into the plot and fight to contribute and make positive change. Possibly the one that leads to the fastest combat growth, but also would run the risk of Agnes being ironically mess-making for a Cleaning Magic user. Or she becomes the golden child for having magic that doesn't cause destruction everywhere she goes. Lots of faces we already know, things to stick our noses into, and weird shit to fight.
[][Guild] "...I want to see a few more places before choosing."
Putting it off. Seeing other options, developing Agnes further with more Guild Master Questions, establishing her base character more firmly.
Gah, it's tough to choose. But I'm going to go with:
[X][Tail] "...Want the world to be safe and good and clean. For everyone."
[X][Guild] "...I want to join Fairy Tail."
My second choice would be Reason to Live paired with Phantom Lord.