Here are the three brushes I use for all my sketching and inking.
9pt Sketch - 70% Grey, 20% Smoothing
15pt Exterior Lines - 70% Grey, 69% Smoothing
10pt Interior Lines - 70% Grey, 69% Smoothing
These are Photoshop brushes, so its an ABR file. If you use different software, you'll need to make sure that it can import ABR brushes.
Importing Brushes:
Photoshop - https://www.adobe.com/products/photoshop/photoshop-brushes.html
Procreate - https://help.procreate.com/procreate/handbook/brushes/brushes-share
Krita - https://docs.krita.org/en/reference_manual/resource_management/resource_brushtips.html
Clip Studio Paint - https://tips.clip-studio.com/en-us/articles/4002