We actually have a specific thread for collecting CYOA, though it fell back a few pages so I'm not real surprised it got missed.
Gotta admit this specific CYOA... doesn't do it for me, it needs a bit more work. There's hints of some flavor to this world but not enough for me to get a feel for it. Is the Royal Family corrupt? Who are the movers and shakers of the organization? Couldn't I get a map of the city to have some idea what it's like? This feels like it needs another page or two to flesh out the world. I'll give it a shot anyway.
Class: Ranger
As I'm about half-blind I tend to gravitate to classes that would let me see again without lenses as thick as my wrists. Animal control is also really, really handy. My first thought was that it wasn't because this isn't taking place in some wilderness but having every pigeon, stray dog, house cat, and cockroach in the city available to spy on people for me is incredibly powerful. If the Royal Family have any Royal Pets I've already got a spy in the Citadel. The CYOA doesn't tell me how big the core is at all but if it's small I could potentially just send a big rat to fetch it back.
Base: Sewers
The house, brothel, tavern, and workshop are all things I could acquire anyway with some funds so I don't want to waste the opportunity on them. That leaves either the undetectable magic treehouse or the sewers. The treehouse is tempting but I don't know if it's completely impossible to breach it's magic defenses, whereas with the sewers I
also have mobility throughout the city that nobody will be able to beat. Combine with using sewer rats as spies and there's nowhere I can't have eyes.
Obviously I'm going to try to rent an apartment rather than actually try to live in the sewers though.
Artifacts: Mysterious Key, Noble Documents
These items all suck. Most of the artifacts don't work with this character concept and in fact can only possibly work with very specific builds. The Gyrocopter, f'rex, is totally illegal and also going to be obviously visible to everybody as you fly around so there's no point unless you're part of the Royal Family and thus above the law. Same with the Mech Suit. The submarine is tempting and I'd go for it if the sewers are actually large enough for it to travel through some main areas but even by the standards of absurdly spacious sewers that's a stretcher. Also on principle, I distrust any submarine that has smokestacks. The contraband tools, money, and alchemy set I can acquire normally so avoid those. The compass looks like it's more likely to get me killed than give me an advantage.
I have super aim powers so taking a magic crossbow would make sense but that's some weaksauce power it's got, same with the prod. Magic Arrows to turn lights on and off? Come on, show me something actually useful.
The Mysterious Key lets me get unspecified magic treasure as long as I brave flesh-eating ghosts. I'll head out into the woods and smuggle in a couple of grizzly bears to act as meat shields as a starter plan, which will change once I have more understanding of how flesh eating ghosts work and how to re-kill them. It's a question on my mind if ancient magical artifacts are worth a rat's ass though. This setting appears to be one with advancing magitechnology which usually means ancient artifacts are curiosities, not all-powerful relics of a golden age like they would be in settings where old magic is stronger and there's no real innovation. Ideally the mysterious woman would let me ask a question or two on that before I take the key. If these artifacts don't seem worthwhile I'll probably just take the cash despite it being a waste, because everything else is a waste too and at least money is versatile.
Noble Documents can't be replaced and it's apparent this is a setting where being an aristocrat is highly valuable. I'll go with them so that I have potential social contacts if I need them, though they aren't going to be my first choice for breaching the Citadel.
Allies: Pagans
I hate all the potential allies which is convenient since the game requires me to betray them. As they appear to be back-to-nature types they should synergize with my animal powers. Summoned spirits sounds like
exactly the kind of thing that would counter flesh eating ghosts so this works well with the Mysterious Key. It's not clear if the Pagans also hate magic treasure or not. If they hate it I'll destroy some treasure in front of them to prove my piety and if the magic treasure doesn't count as a machine I'll contribute some treasure to the church to prove my piety.
Second choice would be bankers since it makes taking the cash redundant, and would almost certainly synergize well with my noble title. This would basically turn me into magical Batman who acts like a wealthy noble during the day and goes animal-themed superhero at night. Actually that might be better than Pagans depending on a lot of information on the groups I don't have.
Either way at this point I have a route into the Citadel, spies in the citadel (unless they can really eliminate every last vermin the instant it arrives, and have no pets), magic treasure of uncertain usefulness, super vision, and trustworthy animal companions. I think my odds are decent.