You can get by with four colors (mentioned elsewhere on this forum). Black (or Payne's Grey), white (titanium covers best), yellow ochre, and Venetian Red. (Venetian Red is warmer than Indian Red). These were the colors of the ancients and were the mainstay of the old masters. You can make any basic color you need from these. These are very good for getting flesh colors. All other colors are eye candy and should be added as you gain experience and master these four.
My attachment shows four high quality pigs bristle filbert oil painting brushes at the top, a sable oil painter's filbert next, a large synthetic watercolor wash brush (useful for a lot of things) and a ratty old watercolor sable for blending. In addition, I use high quality Kolinsky sable watercolor brushes for fine work - #4 and #1. I'm told good artificial sables do almost as well and are much less expensive too.