Another art supply that has been on my shelf for a long time is
Daler Rowney's FW Acrylic Artists Inks. The black India ink is still my favorite black ink, very rich and very dark. If I spot blacks with FW inks and also with a marker on a page the FW blacks will be much, much darker. It is very smooth and clogs infrequently. It's acrylic based, which I think gives it a certain thick consistency without gumming up too badly. It's also the most water resistant ink I've used so far, drying quickly and staying on the paper when I apply watercolour over top. I use the India ink for outlining characters and spotting blacks. In an illustration I may use all dip pens and FW India ink.
I also use the FW white ink, which is pretty good but not perfect. It usually will cover black ink but it's opacity is inconsistent. At least in my experience. Sometimes the ink will go on watery , barely covering the black ink. This usually requires me to stir the ink up again. The white ink has pigment that seems to detach itself from the liquid and settle at the bottom. This can be pretty frustrating. I simply haven't found anything better, so FW white will have to do. I've tried a number of other white inks but all of them lack the opacity of FW, and cover the black ink with a pale see through wash. I've also tried white acrylic paint, gouache and a number of corrective fluids, none of which do the trick. I actually like the opacity of white out but it's so gummy that it's impossible to use on delicate lines, which is what I need it to do. I have found FW white ink works better when using a brush, rather than a pen. So, sometimes I'll use a very thin brush, like a 0 or smaller to apply these lines. If you've discovered any magical white ink let me know!
I should mention that I got my start in choosing the various materials I use from a thick how to comic book by Cerebus artist
Dave Sim. I tried to find it online but it's not there, as far as I can tell. A great comic where he goes through all the practical things you need to know about making comics, right down to the brands he uses, which was very helpful.