What I use most are violet, pink opal, vanilla, cornflower, deep purple, green, chartreuse and golden olive of course.
As for samples, go for it, I usually buy 1/2 teaspoon samples instead of 1/8 or 1/4, that way you actually get a bunch of uses out of em.
Samples are really good when you're unsure of a color.
Or you could wait for the holiday mini pigments...Generally they have some really nice colors in there