For detroit techno style (i assume that you are talking about the Belleville Three stuff?) you should not really dive into modular, since their approach was more focussed on grooveboxes.
But if you want to dive into some more kind of versatile “electro” direction you should definitely go for a classic subtractive synth approach and build up from that to whatever you feel more driven to.
So a simple monophonic synth voice could be a perfect start. I would take a look into 0 Coast (which is actually more west-coastish) or other semi-modulars before investing thousands and realizing that you could do all of that with Bitwigs Grid or something…
I just took a look on your modulargrid: Metropolis + Atlantis is a killer combo, but you might get bored with the filter, so maybe take a look at some filter modules. Since this heavily is based on personal taste it is hard to make suggestions here, but QPAS and Bionic Lester are both stereo capable, very versatile filters: They can both do the “bread and butter” stuff and can get to very experimental and unique fields of sounddesign.
But something that is always heavily underrated: MIXERS! Put mixers in your rack, and put many of them in it
Believe me: You will miss them when you need them, and stackcables are not always the solution.
If you find one, get at least something like an Abstract Data ADE-60 (or something similar), which has a very small footprint and can be used either as offset, mixing 4 signals into one output, trim independent channels and do various gainstaging tasks. I also have one, and I wisch I would have some spare space for another one…