|The unfortunate thing about V!Lilina is that she - as well as most green tome cavalry units - requires a lot of effort to be able to use properly. She's essentially a Cecilia with more attack spread and less defensive spread. Her speed isn't that good, unfortunately, so a lot of the build's focus is to get her speed up to help her double enemy units easier.
Weapon: As her base weapon is hard to use well, Gronnblade+ serves as V!Lilina's best weapon choice. With all of the cavalry buffs she'll be getting on a proper cavalry team, a blade tome will help her put off more damage onto her opponents.
Assist: Reposition is a good assist for V!Lilina, as it is for basically every cavalry team. If you don't have any reposition to give her, Swap can work as well to further her movement range, helping her get out of combat easier.
Special: Moonbow is V!Lilina's best option for specials. Since the blade tome slows your special charge down, low-cooldown specials work best, and Moonbow is the perfect special for blade users. Glimmer can also work well as an alternative.
A Passive: Swift Sparrow 2 is V!Lilina's best A skill by a very large margin. It helps her boost her offensive spread even more, helping her to kill any enemy units she faces. As this is a hard skill to acquire, Darting Blow 3 can be used as an okay alternative, as it helps her get her speed up to double more foes.
B Passive: G Tomebreaker 3 is a very good B skill for V!Lilina, as it helps her do better against other green mages such as Cecilia, Gunnthra and Nino. She can alternatively use Bowbreaker 3 to do better against bow units, but G Tomebreaker is much more useful for her.
C Passive: As with most cavalry team units, Hone Cavalry works very well, but any cavalry buff can be used depending on what your team needs.
Sacred Seal: Speed +3 is V!Lilina's best seal by a long shot, as it helps her get her speed up to double more units.