Sorry pal but the first floyd member to influence Floyd's direction was Syd Barrett.
Ok I agree to a certain extent, the underground music scene in London, the free concert in 1967 etc.
However as Syd became unfit for duty in 1968ish the band brought Gillmore in to play his guitar parts.
As he descended even further into his drugs, the band made a decision not to pick him up on their way to a gig (Southampton). The modern Pink Floyd was born at that moment.
They openly admit they couldn't write 3 minute singles like Syd but could write 30+ minute pieces of music.
If Syd had stayed functional Gillmore wouldn't have joined, and Floyd would never have written Darkside of the Moon, as Waters took over the writing of material after the void left by Syd.
Theres loads of stuff out there on this. I've tried to load a picture of Syd from 1974 but can't.
It really is a crying shame how he turned out, even the band didn't recognise him when he rocked up at Abbey Road studios in 1974 sometime during the Wish You Were Here recording sessions.
I think the second album A Saucerful of Secrets after Syd left was the most influential in Floyds development but thats the Gilmore/Wright influence.
The first time we hear Gillmore/Wright harmonies in the Celiestal Voices part of the track ASFOS.
But hey I like both Syds Pink Floyd and Waters Pink Floyd.
However I haven't supported Gillmore's or Water's solo career I'm not interested it ain't Pink Floyd.