I suggest you to try them. It's a nice experience.
https://www.rohrer-klingner.de/en/writing-ink/?lang=en
About the pens, you can find very nice fountain pens on aliexpress, starting from 4 USD including delivery. For example Jinhao X159, 9019 and 9016.
To have more shading, I suggest M nibs.
KWZ got started as a producer of iron gall inks but has branched out a bit since. But they still have a large range of colors of IG inks, potentially the largest: https://mountainofink.com/blog/kwz-ink
I have some of them, the gold one is a lot of fun as it darkens as you're writing.
If the long-term properties / resistance of the ink are important, R&K also makes one of the few archive grade inks - their Dokumentus. A bit more expensive, but still affordable compared to alternatives. It's nice, but a bit higher maintenance than the Salix / IG inks. I think part of the permanence is achieved by some powder emulsion, so long term storage of an inked pen can be an issue (past maybe a month or so, or even a week in hot and dry weather).