I always do ink first before watercolor.
I highly recommend the Sakura micron pens as they are waterproof, with crisp black lines. They also last a long time.
Also, J. Herbin encre (French ink) is a good brand for ink too. But it's water soluble, so apply it last.
Both products have good crisp lines and come in many colors. I know this isn't a product recommendation thread, but I just thought I'd help you because these are the inks I use a lot when I do watercolor.
Good luck!