Winter: V-necks in full-length sleeves, preferably merino wool
Spring/summer: cotton V necks in shorter sleeves (short, elbow, 3/4) in cropped or longer... cropped length looks best with skirts, dressses and with fuller, longer tops worn over clams (For my figure, at least)
I have crew necks too but I definitely wear the v-necks more often. I also have some scoop neck cardis that are quite fun.
Actually, I would probably focus more on COLOR.... I need a black for winter, and a white for spring/summer. These seem to need to be replaced because the color washes out of the black, and the white gets dirty. Then I need seasonal accent cardis too...