Who should i 1 trick?

Well, there is Kalista..... but she does require a support that has even half a brain as to how to play with a Kalista.

I always enjoy having a good Kalista as my ADC seeing as she has mobility.... some utility..... team work with the support of getting them in or out...... and she can easily just rend a Baron or Dragon after stacking a bunch of spears and "outsmite" any jungler early game and normally late game as well.

She also has an added bonus of added Vision..... you can use your specter inbetween your try bush and red on blue side, or just up and down river.... etc. If it disappears before its time then you know someone is close. It cant be red trinketed.... and it is pretty good bait as well.

Is she perhaps an option of yours?

if you want to climb, one tricking is the way to go.

if its between xayah or ashe, I think you'll see more progress long term with xayah since she is more demanding than ashe.

People typically one trick strong early game champs, but xayah is pretty good too.

Make sure it's someone you love to play.

I'd go for Xayah as you can't really rely on your team to follow up on Ashe Arrows. Xayah has just more fullcarry potential on her own as not only does her strength not rely so much on her team but she also isn't so weak without her team due to her ultimate which provides very decent self peel.