I guess there are two main areas to consider here, namely tools/spare parts and riding gear.
Tools are dependent upon your knowledge in how to use them.
One rider suggested doing all your regular servicing with the tools you carry on the bike.
If you make it a rule to do a pre-ride inspection every day by touching every nut, bolt or other fastener, and other parts you are inspecting, you will soon learn to recognize when something is not right.
Might want to install RideOn tire sealant and balancer in your tires as a preventative measure too.
The more you know and prepare, the fewer tools you need to carry.
There have been members who ran into mechanical trouble on a ride and used their cell phone to contact this board for help in diagnosing and fixing it.
I always carry the tools that came with the bike, along with several more and some wire, tape etc.
After running out of gas once, and not being able to get the reserve to work, I sometimes carry a 1 gallon jug of gas.
Knifemaker once said something to the effect that the only tools he carries now is his cell phone and an AAA towing card.
EDIT: KM beat me to it while I was typing this missive! lol
Dress in layers so you can add or shed clothing to suit riding conditions.
Some other suggestions:
spare riding or prescription glasses or face shield? along with cleaning solution and a microfiber or soft American cotton cloth. (I read that it is softer than other cotton. <shrug>)
first aid kit;-antihistamines, (sun)burn ointment, eye dops, headache pills, etc.
plenty of water
easy to eat snacks like trail mix or granola bars, when you stop for fuel.
Others will offer different suggestions.
After a few day trips you will get to know what you want to carry.