FFX - Customize in early game; First Strike - who gets it?

Update: I gave First Strike to Lulu and it is wonderful! Swap her for Rikku to Steal, swap Rikku for Auron/Wakka to clean up, defend or fight with Yuna and Tidus, steal with Kimahri, then swap back to Lulu to finish off the likely Elemental. I'm excited to get the Sonic Steel for Tidus and then once I unlock Monster Arena im going to beat up Chimerageist and make First Strikes for Everyone!

Recently arrived in Guadosalam and can now use Customize. I have a Return Sphere (blitzball, attack reels unlocked) and I want to give someone First Strike, with the most worthwhile / long lasting results. \*\*note\*\* everyone gets a turn in every battle, Kimahri has Steal + Use and will be going through Yuna's grid. We are pausing at the end of our grids for some theory crafting and testing.

Tidus gets a First Strike weapon soon enough, Rikku is already super fast and I want her to have Alchemy.

Wakka - applies Dark or clears mages

Lulu - uses Reflex and goes away, clear elementals

Auron - Guard before attacks, especially if Ambushed

Yuna - anything? I like her Besaid cloister staff.

Kimahri - quick steal & swap

Who do you think is the most deserving, or will see the best ROI?