My basic claim for Norman is that, if you aren't buying the 4-5 XP mystic cards, then you're better off with Daisy Walker (who has access to Higher Education and tome-shenanigans). Norman's strength is that he can go big - so do it. Go Big, or Go Home.
So I like Shrivelling(5) and Grotesque Statue, two of the biggest and most powerful mystic cards. That's 18 XP right there (assuming you don't Arcane Research), and the core of your power. It means you're a Seeker who can drop the pain on enemies if needed, as well as guarantee key passes on Seeker activities with your statues.
Beyond that, my second point is that every time you use Norman's ability, its the equivalent of drawing a card and possibly gaining a resource, so its almost 1-2 bonus actions (ish). In other words, you want to use it as often as you can, every turn if possible. This means he favors events and assets over skills (you can't use his ability to commit cards), and favors lower cost "stuff" that can be played in most situations.
So Working a Hunch, Mind over Matter(don't save it, just use it), Magnifying Glass(0), No Stone Unturned - all these are better for him than for others. Even Emergency Cache and Shortcut are better, as they are playable from the top most of the time, netting you +1 card. Value.
Beyond that you've got St. Hubert's Key and Dr. Milan Christopher or Alyssa Graham. Dr Milan is the best, as always, but Alyssa is still pretty good for Norman, so you could be generous and let a teammate run Dr Milan (maybe even Finn if you are feeling very kind) . The Holy Rosary I feel is a bit of a trap. Despite all the Purple, Norman is still a Seeker at heart and will be Investigating a lot. +int is more valuable to him than +will, and therefore the Key really delivers for him. Plus you're probably not running Arcane Research and your mind is still healthy (ie, the Key sticks around longer).
All of this is standard Norman, irrespective of the campaign. For FA and others where the encounter deck can be rough, I do like Scrying(3), though Mists of R'lyeh is also a fair call for the second Arcane slot. Between them, Ward of Protection, the Statues and potentially other cheats like Counterspell and Time Warp, you should be OK. Dr. William T. Maleson and Seal of the Elder Sign are possibilities too, though you sacrifice a lot for them in terms of the Ally slot or XP. I do also like Protective Incantation just to burn some of the Dr. Milan Christopher money (no Higher Education remember) and FA, on any difficulty, has some pretty horrible tokens in the bag worth sealing. I'm less keen on the Spirit Athame or Crystalline Elder Sign. The latter is a solo card for me, no good for 2+. The former is for pure mystics... Norman should be using his Intellect for searches 75% of the time, with his spells coming out to save the day at key times.
Mystic splashes for me are then Ward of Protection, St Hubert's Key and Delve Too Deep (rotating out once you have XP). Alyssa could sub for one of these if needed. Ideally you want 2 of all of those, so you have hard choices at the start which to drop to 1. It gets easier once you drop the Delves, or on Standalone where Delve is not needed. I try to avoid starting with Shrivelling, as then you are paying XP to bring in your level 0 purples once you upgrade the Shrivelling (which you surely want to do). This means you are probably leaning into Shrivelling(3)/Shrivelling(5) as your very first upgrades then, and running a couple of games building up to "Maximum Firepower!".
I haven't talked much about his Signatures - and to me, they are not that important. His unique deckbuilding and game ability are far more defining. Split the Angle is a bit iffy. If you run Scrying(3), or Alyssa Graham, it sometimes has value, particularly in encounters with obnoxious cards, but even then it's often worth chucking. Without either of those, its just not worth it, and you should never be using the first "waste an action" effect, even on solo. The Vengeful Hound is extremely annoying yes, and you can draw it in the first turn before any actions (truly as horrible as it sounds), but beyond that it's just a bad-guy. Kill it or get your friends to help kill it, then move on.
My one complaint with Norman is that he can feel a bit slow-and-steady. As he often spends a lot of time dropping assets and events, and as he doesn't have access to Higher Education, Pathfinder, Shortcut(2), Deduction(2), In the Know, etc, he doesn't dash around the board hoovering up things really quickly like Ursula or Rex (or Daisy/Minh if you build that way). You just need to let your teammates know that. But he makes up for it by turning up to boss-fights and times of stress with virtually unshakable destruction, as well as being efficient and value-driven in his cards. I really like him, he's quite unique.
I feel Investigator reviews should put their money where their mouth is with a sample deck, so here is my Norman that I've been using for Standalone scenarios.
Standalone Norman - Go Big or Go Home
