Hmm, something I just realized that I like about Garuda as an eidolon is that it has a rather generous floor to it, setting aside the fact that dual element will have the lower longterm ceiling. For wind/water, via story and events, you get access to:

Nike (water) - healing, A-frame +12% defense buff with *
Cybele (wind) - Mistletoe Drain (B-frame -15% attack and defense debuff with *)
Heimdallr (wind) - Horn Ale (party A-frame +10% attack buff)
Gabriel (water) - A-frame -12% defense debuff with *, B-frame +12% attack and defense buff to party with * (it's a B-frame version of Ramiel's Rising Heart, essentially)
Nodens (water) - inflict drowning to one enemy, weak regen, remove one debuff from party
Guan Yu (wind) (from some sort of Koihime Musou collab event, dunno if we'll see it?) - attack buff to party (probably A-frame, but not listed on wiki), inflict poison to one enemy
Krampus (wind) - attacker with a Raging mode specific nuke
Cupid (water) - try to inflict dazzle to one enemy, defense buff to party (unlisted frame, presumably A), fire resistance buff to party

So you can roll complete garbage, as in literally no SR/SSR kamihime ever, but still piece together a wind/water team that can at least somewhat fill all the basic needs at an acceptable level with double Garuda to prop up your attack.