The keyword in that title is YOU. A landscape painter needs different colors than a portrait painter. So in order to find out what works for YOU, I suggest you start by finding out what you already have.
If you take the time, maybe two hours or so, I PROMISE you will have epiphanies that will result in you choosing better pigments that you LOVE and that work for you. I even promise that it can be more fun than you anticipate.
Here goes:
Pull out every oil paint you have
Cut up some strips of watercolor paper
Glaze each strip with a light coating of acrylic medium. (Ok, so watch your fave tv program while all this prep is happening, the real fun hasn't begun yet, you're right.)
Get out your palette, a brush, titanium white, and a marker.
Mark each strip with the Mfg name of the pigment, underneath that, the brand of paint, and under that, the pigment code. Don't leave out the pigment code!!
Special thanks to Janet for posting her gorgeous fan color deck!
https://watersolubleoils.forumotion.com/t240-paint-swatch-fan-deck?highlight=color+swatchReady?
Here are some pictures, A-HA's and results of my color swatching today. The pictures are quite large so I'll keep them hosted at my site. Enjoy!
http://www.artforthesoulofit.com/2011/02/04/choosing-a-palette-of-watersoluble-oil-paints/