This is my typical palette if you also include Titanium White.

I like the limited palette because it makes life easy.  The simple questions become: lighter? darker? warmer? cooler? Not - Which blue,  which red or which yellow? It just works for me. I can imagine that my palette will grow with my ability, but perhaps not.  I like the simple approach.  (Colors include naples yellow, cad yellow light, yellow ochre, orange, cad red light, cad red deep, venetian red, cobalt blue, ultramarine blue).

I always mix my greens.

Sometimes I use a medium of 1 part Stand Oil/4 parts Terps.  If I want 'extra juicy' paint (as in highlights), I will use Gamblin Galkyd gel as a medium. 

I also always brush or wipe my canvas down with linseed oil before starting to apply any paint.