I love the pose! And as @scrawly mentioned already the blue-ish/gree-nish color on her clothes turned out great.
As they say - Practice makes better and with some more attempts you will get the hang of it. But yes, some variation will do you wonders xd you can always come back to it at some other time. Or maybe just try inking fully in one colored ink.
Hmm, have you thought about maybe getting a fountain pen and using india ink? Maybe you can also use water soluble ink to achieve monochromatic pieces with the help of some brushes. I think you will be great at it!
imma look at these fountain pens thingy.... are they expensive? :O thank you for suggestions and feedback <3
Not really. Recently I watched some youtube reviews of comparing expensive brands with their knock off which some Chinese companies sell either on Wish or Aliexpress and they came quite close to originals as a result. I think for 4-5 dollars you can find a decent one. I will recommend you checking few videos, so you can see also how it goes as a medium and if it will even work out and suit your preference and style
In regards to ink I haven't researched much, but there are all sorts of colors, metallic inks, neon ones, with sparkles xd I myself have only white india ink for adding highlights to my drawings.