You'll probably want to basecoat in acrylics if you're going to shade with oils - it provides a smoother, flatter surface and doesn't run the chance of melting when you shade like it would if you used enamels.
Your starter colors should be white, black, raw sienna, burnt umber, raw umber, naples yellow and yellow ochre for faces and plain red, yellow and blue for maixing uniform shading colors.
I'd recommend Winsor-Newton oils, they are the best you can get. The artist oil colors are best, but they run about $15 to $30 a tube, so if you're not a millionaire, their lower-priced Winton Oil Color will do fine.