Painting walls a dark colour: Tiefengrund or wall primer?

A question for the DIYers out there: I want to paint a room a very dark colour. The walls are brand new and are drywall (Gipskarton) that have been patched and sanded. My first instinct was to buy a (grey/dark) primer to prime the walls, then paint them with a high quality paint. It seems like this is not a thing here, and most websites [recommend simply prepping Gipskarton with a clear substance called Tiefengrund](https://www.malerpraxis.de/arbeitstechniken/streichen/gipskarton-richtig-streichen-mit-diesen-tipps-gelingt-das-renovieren-muehelos/) that evens out the Saugverhalten of the wall, then painting directly on that after it has dried. The only wall primer I can find is from [Brillux](https://www.farbenkönig.de/detail/index/sArticle/66900?sPartner=gs-farbig-brillux&number=BX3729RAL7001&gclid=Cj0KCQjwpeaYBhDXARIsAEzItbEtB1NyImaNOybdMvnfVcU3BnaG0B9ragKXtKIC4IoWgJDjk09QX-QaAsUzEALw_wcB) and is really expensive.

Does anyone have experience painting a wall a dark colour? Is the Tiefengrund enough? How does it compare to what in the English-speaking world is considered a primer? Nice paint is expensive, so I’d really like to use it as efficiently as possible.