Further to my previous post, you may want unbalanced version.
I believe they have stock.
Having said that, I just noticed someone suggesting MI Veils which I think is a great (honestly better) idea. It can boost line level signals, can mix to a single output if desired, and it much more flexible.

(May be currently sold out, have a look here under ‘External’ modules. NW2S does have a website.)
8 inputs and 8 outputs each to a separate Db25 connector. You could get an 8 x 1/4” to Db25 snake to connect them. Attenuation +/- 6 dB is done within the module. The module and snake are a bit of an expense but then you are able to combine what you already have and keep using it with your new eurorack setup. The 8 outs could also be routed to an audio interface onto separate tracks in your DAW.

I would start with a more traditional setup to start.
1) VCO's, one or two to start, analogue or digital. With more than one, you can stack and cross modulate. I would also get a noise source. Make Noise STO is great, flexible and reasonably priced.
2) Filter, many different styles, low-pass to start but there are many multi-mode filters that do lowpass/ bandpass/ highpass simultaneously. Modulation of a filter can make your system sound like two or three simultaneous instruments.
3) VCA, I second MI Veils and Intellijel Quad VCA. WMD has the Javelin which is a full ADSR with integrated VCA and separate envelope output (great 'bang for the buck').
4) Function generator, Rise/ Fall will do envelopes on a one-shot basis or will loop as an LFO. Maths is great as is Intellijel Quadrax (4 rise/ fall, but no mix and Or/ Sum/ Inv).
5) Output module, L/R 1/4" Stereo out + 1/4" Headphone Jack (you need a means of listening to your results and get them out of the box if that is your intent). I have a WMD and Befaco but there are many others.
6) Additional modulation: Random generators, Touring Machine is great. Sample and hold (often good for a noise source as well).
7) FX. It may seem like a luxury to start but a nice reverb or delay can makes things sound huge and otherworldly. I second FX Aid as a start.
8) Mixers are important but you have only two signals to mix in your current setup. I use Befaco STMix for submitting as it will mix 4+1 stereo signals (or mono normal to both channels) and is DC coupled and will mix CV. There are many others.
9) General utility, Multiples (buffered? or not), attenuators (Synth Tech modules have onboard attenuation so perhaps not as big a deal to start),
Synthesis Technology E352 Cloud Terrarium probably wouldn't be my first choice to start but if you want to go that direction, what ever will keep you motivated and interested is important. Mantis case is a great start. Good luck!

Think of it in terms of signal flow.
Sound sources: DPO is a complex oscillator and not cheap, but great value. You have independent waveform outs and V/Oct, you can stack the two Osc. and more importantly (in the long term more interesting) you can modulate one with the other and cross modulate. You should also have a noise source as well.
Filter: Mono or stereo, style to your personal taste, low pass only or multi-mode? I probably wouldn’t pick the Rossum filters to start, although they are both great. For mono, I love the Synthesis Technology A440 (low pass) and I have the the Bastl Ikarie which is a high/ low pass with a drive circuit to add filth/ saturation. There are tons of really good filters, it really is a matter of taste…
Envelope: WMD has the Javelin which is a full ADSR in 6hp with a built in VCA. It also has an envelope out. Xaoc Zadar is awesome because you can dial up all sorts of envelopes so quickly, with some being quite complex.
VCA: Veils is great, very useful and compact. Intellijel has the Quad VCA.
Modulation: Xaoc Batumi is a great quad LFO, I highly recommend it. You can’t argue against having Maths but I personally don’t have one. Quadrax is ultimately more flexible than Batumi and is what I would probably choose. Mutable Instruments Stages is great as it can be a multi-stage, one-shot or looping envelope, or even a CV sequencer. You can chain them as well.
FX: I would go with the Morphagene as a delay because it has so many sweet spots, is easy to work, and has what is essentially a reverb built in. FX Aid is a great bang-for-the-buck multi-FX and flexible. The Erbe Verb is not a conventional reverb but rather a thing unto itself. Not my first choice to start.
Utility: Pamela’s New Workout should be in the first round of modules you buy with 8 separate clicks/ modulation sources. Mults, buffered multi, adders, sum/ diff., logic modules, attenuators ( 2hp modules are great, but can be a bit crowded and tight). Also random + sample & hold…
Sequencer: Intellijel Steppy is compact and great to start with, but will only do triggers, not CV. Do some research and use your system for a bit before you settle on a sequencer as each one has it’s own workflow and strengths.
Overall, I would start simple and make your larger investments later when you know what you want and you have the skill and experience to take advantage of more complex (and expensive) modules. (Verbos modules in combination have tons of (often narrow) sweet spots which are not always easy to find and they are expensive, not great to start out with) . Good luck!

Working outside in, I’d suggest you consider the following:
1) As mentioned above, a potable audio recorder (Zoom, Tascam etc) is your best bet for recording. You can also make field recordings with it and bring them back to your system.
2) There are great output modules (I have a Befaco, WMD, Joranalogue is great) and they usually have a headphone out as well. You can have a separate input module if you will be importing sounds or a combined I/O module (eg. Intellijel I/O).
3) You will have to look at a mixing solution that feeds into your output module. Befaco STMix is a nice 4+1 stereo mixer that will duplicate mono L to R, with level control, DC-coupled to mix CV but no pan control. If you eventually upgrade your mixing solution, you can still use it for sub-mixes. Next level up would be a larger mixer with pan control and Aux Send/Return (eg SSF Vortices). The top end (expensive) solution would be a Befaco Hexmix + Expanders or a WMD Performance Mixer (I have one, it is f***ing awesome and transformative).
4) You could mix outside of eurorack as mixers can be quite inexpensive, but then you would have to bring all of your eurorack level feeds down to line level which is not practical. Sorry for the length of the reply. Good luck