With Sera I can see her going one of two ways.
Number one, she’s a perfectionist. So she can try to be useful and give us a book to boost a skill that isn’t quite there yet. As a perfectionist though, it would make sense to make it a skill that actually has some points in it. When we have combat 1, a book on jeet kune do or whatever would only make the MC only slightly less useless after all.
Number two, ritual magic seems to be a passion of Sera’s. If she wanted to share her interest with the MC, she might give the MC a book on ritual magic hoping they’d become interested. That being said, if the MC isn’t any good at ritual magic, Sera could offer to tutor us. If we are good at ritual magic, then it could be an overture to become study buddies.
Possibly make it tied to our Sera relationship score if she just sees us as someone who needs help or someone she’d like to spend more time with/be better friends.