Tried my first rack here, would go for a mantis rack.
I am interested in experimental, dark, droning, sampling, granular, techno, ambient, wavetable.
Had a Waldorf Iridium before and would like this in analog/modular.
Would you change anything? Do I have to take care of anything?
Or should I rather buy a Shared System used for €3500?
Or a Black System III ?
Or should I start smaller (nifty)?
I would sometimes like to use my digitakt as a sequencer/sound source, is it possible with this?
I am no technician and have two left hands :)
Sorry for all the questions.
But I love music...

I recommend the Erica Synths Black System III to start with if you like the demos from the Erica Synths modules. I have a lot of their modules and love them and the Black Sequencer is one of the best modular sequencers and user friendly for beginners. That said, I also have the Make Noise Shared System and enjoy that but it is better suited for pure weird experimental type stuff. Erica Synths is more focused on techno and dance style music but can do ambient as well. Make Noise takes effort to make dance techno music. BUT half of the fun is building a custom instrument from different modules versus an all in one system from one company like Make Noise or Erica Synths. I started off two years ago with a Doepfer A100 Basic System 1 based on recommendations from my modular synth friends in southern California when I was brand new to modular and also because at the time there were no Make Noise or Erica Synths systems available for sale at the time. It was helpful and good Doepfer modules sound great and easy to use. I added to the case and now have different brands. Also check out Verbos Performance System they are expensive but analog and sound incredible. Building own system is the most fun however and best learning process.

Thank you, much appreciated. I like the sound of the Black System III a lot and I am really into dark techno stuff.
The Shared System looks nice and shiny and sounds good to my ears. I enjoy putting modules together but I am overwhelmed by the choices.

The Erica Synths Black System III or Techno System would be my choice.

You're not going to manage an Iridium/Quantum in modular. Polyphony in modular generally results in huge systems, as you need a massive amount of repeated modules in groups...for starters. Same VCOs, VCFs, VCAs, LFOs, etc etc. Oh, and it'll have you ripping your hair out while programming it. But then, this isn't really what modular is about; you want to build something in Eurorack that is capable of stuff that only a modular can do, just like a Waldorf synth does what THEY do.

The Mantis is a good starting choice, as it can easily be expanded with a second Mantis + the link brackets. Also, the current capacity of the P/S is beefy. But the build above is just not going to work...there's too many really big modules in there in space that could be better used by smaller modules. That way, you can have some elaborate capabilities that, right now, this build isn't capable of.

Lessee here........OK...hmm, not bad:
ModularGrid Rack, I coupled a sampler together with a VERY complex harmonic oscillator. Yeah, just one...and given what it's capable of, one is all you need! Let's have a look...

TOP: OK...I improved on the MIDI interface by putting in one of Hexinverter's Mutant Brain interfaces. 12 gates, four CVs, with a nice bit of flexibility. Then the Xaoc Odessa oscillator, plus a Hel, the four-voice poly you can have some polyphony until you hit the VCF, which gives you paraphony. A pair of VCAs is after this, with switchable response. Then that little black sliver is a pair of rectifier-type waveshapers, so that if you want to "nasty up" the Odessa, just run its VCAs through that. Then the multichannel sampler, which here is a Squarp Rampler...this saves space, and it makes the sampler a lot easier to deal with since you only have four outs. After that, there's a Veils which gives each Rampler channel its own VCA. Then to sum all of the VCAs down to stereo, there's an Omsonic UPE, which is a unity gain mixer with panning across six channels. With the audio signal now in stereo, I went with a Xaoc Zagrzeb, which is a stereo multimode VCF with all modes "hot" and in stereo. This filter also allows some weird things, such as putting a HPF on the left and an LPF on the right so that sounds can "migrate" across the stereo field, plus a lot of other potential mayhem. Beads goes in after that, then a Happy Nerding FX Aid XL for typical processing, then this feeds a Happy Nerding Isolator, which transformer-isolates your outputs so that you can avoid ground you can hit it hard with the audio signal to get a nice bit of transformer saturation.

BOTTOM: A Doepfer noise/random/S&H module starts this off, then I swapped the Benjolin for a Wogglebug. Similar sort of idea, but more space-sensible. Next, the Make Noise Tempi/Rene mkii combo provides a similar sequencer environment to the Erica, but with a LOT more timing tricks as those two modules are designed to be used together, unlocking some hidden bits that a backplane connector between them uses. Then Maths, followed by a Tenderfoot triple attenuverter/mixer for CV and modulation signals. Another dual VCA like in the top row is after that to provide level control over modulation signals. And last, an Intellijel Quadrax/Qx combo lets you generate basic envelopes...or complex composite ones. Or even more if you crosslink them with the Maths.

That's a better use of space, I think. By doing this, it opened up more space for more functionality without having to resort to having itty-bitty controls for your main modules. And going with the Rampler will be easier to deal with than the Bitbox, which would require quite a bit more in utilities, etc to use to its best advantage. And the Odessa only seems to just be one oscillator...which it is and also isn't. Xaoc stuff is generally very feature-rich, and this is no exception. And hey...I came up with a sum that's only $50 off of your own, but this'll do WAY more for your money.

Lugia is 100% correct and I learned the hard way well at least my 6u Doepfer A100 Starter system was helpful to learn the basics but I ended up expanding to a monster case that really gave me breathing room and then added tools and support modules.

However with that said, new polyphonic modules like Knobula Poly Cinematic and paraphonic modules like Acid Rain Technologies Chainsaw and the Supercritical Demon core oscillator give me hope to at least add to a polyphonic type setup in modular but it still costs way more since you need a good sequencer which is expensive as well as nice big mixer, support modules, effects and so forth. Heck the Waldorf Iridium is a bargain compared to how you will end up spending 5x to get close in Eurorack. If polyphony was a hard stop for me, I would get the Waldorf, Prophet 6 or Access Virus TI2 and a cheap drum machine and be done with it. Same goes for modular drums, very expensive!

Thank you for this very informative and useful advice. I will reconsider my rack and delve into it a bit more.
Lugia's rack looks very good and makes sense, unfortunately I understood only half of what you wrote as I am new to modular.
Would you rather buy something Lugia's rack or go for the complete set and live with its limitations for a while?
I know that at some stage I would change modules in the Black System III for example as it seems rather directed at those who want to have traditional substractive synthesis. I am missing ways for experimentation, unknown chaotic sounds, generative weirdness... please correct me if am wrong!

I have the opportunity to buy a used. Shared system black + gold for €3700, should I go for it?