I am certainly an ATGATT believer and from my assortment of gear, I will chose my riding gear based on the bike I am riding, duration of the ride and weather conditions but will always include the following from head to toe:
Full faced helmet (occasionaly an open face for rides of very short duration, such as over to a friends house in the neighborhood)
Armoured jackets of which I have several ranging from leather with soft armour (touring) leather with hard armour (for sport riding and track days), Waterproof styles for touring, GS'ing and cooler temps and mesh with armour for summer.
Back Protector for sport rides and track days.
Protective gloves, too many styles for all riding styles and conditions. I always ride with at least 2 pair (one waterproof just in case) with me sometimes 3.
Armoured pants in same combinations as jackets, plus I do use Draggin Jeans for casual rides.
Armoured boots, I use different ones for toruing, sport and casual rides, but all have ankle & shin protectors.
I have most of my gear lined up on a rack in my garage next to my bikes, which my non riding friends have dubbed the "Bat Cave" as they don't understand why I need so much gear in so many varieties.
Still looking for that one do-it-all riding suit that will be warm in winter, cool in summer, dry in the rain, breathable in the hot, while being protective, comfortable and stylish. In the mean time I will use the myriad of combinations from my collection which usally guranttees that I have the wrong gear on for any given weather condition.