Sets.
However, I did order a very large amount of ball joints and sockets for mecha recently from BrickLink.
Bricks and minifigures because they have a large bin full of bionicle parts and tons of random pieces from incomplete sets
I get most of my new pieces from lego’s bricks and pieces service. They redesigned the site as they are opening up a new warehouse in north america. The recolor selection is very poor right now as opposed to their old european site but hopefully in a few months everything will be back up.