If you have the option to buy cardstock in larger quantities, that might be best (since I'm guessing you can save some money on buying a larger quantity).
I personally love picking out patterned paper s individually, since the few times I bought a kit/package it always only came with HALF of the pp I would want to use.
If you enjoy buying kits/packages of patterned paper , then by all means keep doing it!
Whatever works for you. :P