My best advice is work in a multitude of mediums.
That is why I have painted in just about anything that you can actually paint in. Ink was one the first mediums that I tried after I worked in oils and acrylics and it was a lot of fun. But it felt like I needed to learn more with ink than I did with other properties. The physical difference between inks and paints is that paint is a liquid medium with tons of tiny flecks of solid pigment suspended in it.
Inks are a liquid medium with a liquid pigment.
So ink can be thinned down virtually forever and can be used to mix with the liquid base for paint to produce interesting effects.
One thing to be aware of with inks is if you are using them to do layering/shading you can get bleed through if you try to cover them and they are not /completely/ dry. They're translucent paints you can use to to help "glaze" strong colors over the top of other paints without destroying the light and dark tones. Inks are pretty translucent and they will not darken the area in the way that washes do.
This is why I will still mix in ink to make final piece. It was this major moment when I relied how easy it would be to darken an area for painting shadows. I simply use a wash. If you want to change the color of an area without darkening it, use an ink.
And if you wonder what type to use, India or Sumi-e, remember; India ink- bottles, has a better consistency to it than Sumi-e, it is also generally darker although this can depend on the brand. But it does come in more colors than Sumi-e. The colors are really concentrated so they look very bright and crisp. If you need it to be more dull and muted, simply add water to it. Forget the sumi stuff.