I have 100+ improvised techno jams that essentially documented my modular journey. Modular is very individualistic, but maybe I can makes some recommendations that would save you some time and money. I have also circulated over $100,000 of modules over the last 3-4 years, I've had everything from a full set of Mannequins, QMMF-4...a bunch of stuff, more modules than anyone could ever want or need. The goal of my rig was to be able to walk up to it and go.
These are my favs from the whole thing:
Mixer: WMD performance mixer (V2 is coming out by the end of the year and it blows V1 outta the water it's a gamechanger)
Bass drum: Modbase09mkii into Fold6. I also like Bass Drum 2 alot.
Hats: The best hat will be the AMMT Hi hat no contest. Patching Panda Hatz v2 was great for analog hat. I used Pico Drums for hat samples.
Snare: I preferred an analog 808 and used the Noisy Fruit Lab 808 snare
Clap: Erica Clap, could get to a the more minimal side with an envelope/vca
Ride: Started with Erica Cymbals, but accomplished the same with Pico Drums.
Toms: Erica Toms or Pico Drums cause all of the toms modules are huge.
Lead Voice: Piston Honda MKIII, Verbos Complex OSC. Erica Bassline for 303.
Sub Bass: SY0.5
Delay: Sarajewo (this is one of my fav modules all time, sounds incredible)
Reverb: FX Aid, Desmodus Versio
Master bus: TriTone for EQ+ Saturation, Overseer/SCLPL for DJ filter, MSCL master bus compression.
Other: Natural Gate, Sinc Bucina, Kermit MKIII.
Pitch Sequencer: Ornament and Crime with Logarythm branch of Hemipshere Suite running TB3P0 (random instant 303 sequences). I would've been interested to check out the Precision Disruptor, but didn't get a chance. This would likely be better than the TB3P0, but of course is huge.
Drum sequencer: Metron, Varigate 4 or 8, Erica Drum Sequencer
Master clock: Pam's Pro
I went from a 104 7u to 18U of Doepfer Monster cases, and have used as little as 42hp 4u to accomplish the same things, drums, voices, mastering and all. It's all in the playlist. This is all Detroit/Acid techno kinda vibes sometimes minimal. My approach was to do it as fast as possible to jam every day. I think the modules you get will depend on your goals. Do you want a noodle box for sounds or do you want to smash out beats? I've heard a lot of modulat techno setups, but I always chased a heavy sound...it had to be fat. The most fun I had was exploiting modules to their max like Pamela's Pro Workout and Kermit. I could sequence drums AND synth voices with Pam's. Did you know there's a way to turn Pam's into a Turing Machine? Stuff like that...The biggest mistake was buying a new module to solve a new problem, when I in fact had solutions already in my setup.
It's very individualistic, but the only way to truly know is to have a module in your case and patch it up. There's no reason to buy all of the stuff at once either. I listen back and I preferred my sound back when it was stripped down vs the monster setup. You said you have Octatrack already, try and use that for drums to start with and then just get a Pam's and build up a synth voice to your liking and see how that goes and expand from there. That was the best part! Hope this helps best of luck!