There are a thousand roads to Rome, this list is just one list of workable supplies. I have used other supplies in the past, this is what is currently in my plein air oil painting backpack:

A field easel.  I am currently using “daytripper” easel and a Dolcia tripod. It has a wonderful large pallette and is super simple to setup. I have used: a Jullian easel, and several different pochade boxes. Like most plein air artists I am always looking for the perfect setup. Trade offs are size, weight, and ease of set up.

Apron, and sun hat, sunscreen, bug spray, water bottle, packaged snack.  Layered clothes to keep warm or cool. It is MUCH harder to paint if you are uncomfortable so I work hard to keep myself comfortable.

Flat bristle brushes sizes #8, #10, #12 – Rosemary flat classics are my favorite A palette knife.

Paint – a minimum viable set would include a large tube of white, and at least (red, yellow, and blue)

My colors vary. My staples include: aliziran crimson, cadmium red light, cadmium yellow light or azo yellow, cadmium yellow dark,  Burnt Umber, ultramarine, cerulean blue, sap green. There are many Optional colors, If you buy one more I would buy orange, and king’s blue. Then turquoise blue, quinacrodone rose, greenish umber, yellow ochre.  I usually use Rembrandt or gamblin brand.  Van Gough is passable.  Pliers to open paint tubes.  I use mine almost every day.

ODOR FREE mineral spirits and a jar or something to put it in- I use gamsol and a turp jar made for cleaning brushes, it has a wire insert to allow paint to settle to the bottom and give you something to clean your brush on.  You can also use gamblin solvent free gel, and you can fly with the gel (I use both the gel and gamsol to wash my brushes).  

Paper towels, or Kleenex, or rags (i use a chord or bungee to attach to my easel – a good thing to figure out in advance).  Some small bags to put trash in, I use a pop up trash bucket that I hang from my easel.

I like to wear disposable gloves

I use linseed oil soap to wash my brushes.

I use something called a palette garage to preserve my paint.  It saves paint and time in the field. No waste, and it allows me to pre squeeze my paint before starting. A Tupperware, or Saran Wrap would also help keep paint fresh.

Panels and wet panel carrier to fit those panels.

I like working small and doing many paintings, rather than fewer large paintings.  I am currently working 8×10, 8×8, 6×8, and 4×8 size.  I can store them all in the 8×10 panel carrier made by raymar.  I work as small as small 5×7.  A really good painting day for me is 4 paintings a day.  The most I ever Painted was 12!  I love raymar panels, but they are expensive!  I usually use something cheaper like Centurion.

App: ‘Notanizer” $2 for android and iOS 

I carry notecards and markers for value studies. They are also useful for making painting notes (time, location, title etc) I use blank Notecards, a black and grey marker, and a pencil and pen.  I also keep a small roll of tape to tape notecards to the backs of panels. 

I put all of this in my Kelty backpacking pack. I like having a big enough pack not have to cram. I also like having a good waist belt to help me carry the load down the trail.

I find these kinds of lists interesting and helpful. Perhaps it will inspire you to go out and paint!