Replace the o-rings.
Clean everything and lube with ( I use silicone grease ).
Clean the diverter.
Clean and even sand or use a brillo pad on the inside of the spout, wipe it clean and grease the inside where it sits on the post.
How old is that cartridge?
Why not change the cartridge while you're there.
Maybe replace the aerator or at least take it apart and clean it.