Most artists are also very fussy about their brushes – the springiness, the shapes, etc. I am as well, but cannot afford really expensive ones because I am very hard on my brushes. And of course I often paint with, and scrape away with, my painting knife. And do try out different grounds--- besides canvas (and do you prefer cotton duck or the finer more expensive linen?) there are boards--- masonite, clayboard (which I love), etc. The paints work differently on all of them. And try painting oil sketches on gessoed paper for a new experience.
Basic Palette--- where I try to have a warm and cool shade of the basic colors--- red, yellow, blue, green and brown I could indeed use only these colors for any painting. But often I don't.
Raw Ochre of my past
Prussian Blue now known as Pthalo Blue as well (any brand)
transparent green with yellow undertones
I am told I should have Chrome Oxide Green and Sevres Blue (Rembrandt) but seem fine without them.
Optional Greys --- And just because I am lazy, I do often use one of the other greys--- don't tell anybody
Old Holland Warm Grey light
(Gamblin), and sometimes Red Madder, and Quiniquidrone Red
And after a tip I have just ordered Gamblin’s Manganese Blue Hue — a cool (toward green) transparent water blue and their Phthalo Emerald — a warmer, more natural looking Phthalo Green. I just ordered them from Cheap Joe’s Art Supplies.