You can just click sort by highest % when you are in that menu, but you don't need to level highest, it's very easy to hit 360% or w/e you need for max bonus.

Best links to level in general are units that are used in bond skills for other ninjas since they have two purposes, also basic Naruto/Sakura/Sasuke have good links with most characters, ones you get from story/sweep when you start not the ones you buy for coupons.

Huh i didn't even have this thread open but it replied to this one for some reason and can't edit it or delete it now, that was meant for the one about Kushina BTs.

And Kushina has gotten kinda rare now, they seem to have replaced most older ninjas in events so you will probably want to spend coupons to get her now, instead of trying to collect for free.