After one year I have now filled the last hole in my rack. It happends to be with the Monsoon from Michigan Synth Works.
I just want to thank all of you that have helped me chosing the right modules by your comments to my posts.
A special thanks to GarfieldModular, Lugia and Ronin1974!
I have also learned a lot from the Youtube channels:
My own choice for just three module are Marbles, Plaits and Maths.
I think you can create incredible patches with just theese 3 modules plus the standard utilities.