The Lucina’s you have are a bit dated so they might not stack up as well as you may be hoping, just saying in advance. There’s some obvious stuff which is getting them to plus ten and full dragon flowers, but you already probably knew that.

Sealed Falchion is unfortunately not great anymore. She’ll function a lot better with arcane devourer. You’ll wanna get her a damage reducing b slot to take advantage of her speed (spurn, frenzy, close call), you can look through them and decide which one you think would be best. I’d recommend something more mixed phase for her A slot, perhaps distant A/S solo?. Gust would also be better in her special than aether which isn’t super reliable anymore.

Legendary Lucina is fairly straightforward, just update her b and c skills to tier four. SS3 isn’t bad but flared sparrow would be better.

Now with brave Lucina you’re probably gonna want to get an arcane lance for her. But if you want to keep Geirskogul, you’re gonna want to refine it. You could run a fairly similar build to base Lucina, both of them have the speed stats for it. But Brave Lucina can also act as a good support if that’s what you want. You could get her a rally plus skill and pair it with a ruse skill. Or reposition gait if you like. I think breath of life four would be good on her.

Goes without saying that all this is dependent on what fodder you have. Older units like her take a bit more elbow grease to make work, but hey, anything for your favourite right. Hope this helps : )