I'm totally loving my Viva pens and even though I have all of them I do find that there are certain colors I reach for the most.... Ice white, cream, and Dark Brown! The kiwi also seems to match a lot of things and I also use the Magenta and Turquoise quite a bit. But I use a lot of bright colors in my projects so those work for me!
I'd say start with the neutrals to get the most use out of them and then go from there!
As for drying time....it really depends how big you make your pearls. Very small pearls can dry in about 20 minutes, but the large ones can take about an hour or more if you make them really big.