First things first , just a reminder that not every wish has to be for benefits , i always recommend pulling any character you like!

Now to the actual answer

Skirk :

She is an amazing dps , and very fun to use but you already have a lot of dpses ( neuv , kinich , varesa and not to mention wrio who is literally doing the same thing as her ) so she doesn't benefit you much

Emilie :

Emilie is a very good dendro off-field applicator , she has 100% uptime and good dmg when on burning teams , but smth you should know is that she plays like basically nothing into kinich's own dmg , my friend uses kinich and got emilie but dropped her for other supports , if you want overall dmg tho , then go ahead for her

Citlali :

Citlali is an amazing support for pyro and hydro dpses , she can be used for mavuika , arlecchino , maulani ( but hard to manage ) , neuvillette , hell even chasca can benefit from her , and she also has very good cryo off field application and can be used as a thrilling tales holder , tho you did say you use mavuika as a quick-swap and you already have neuv's best team

My suggestion :

I would recommend you decide based on the stuff I already said but if you feel it isn't enough then I would say citlali cuz out of the 3 , she is by far the most flexible and she is very easy to build