1,5 years ago I started the same route and guess what my first module was? Clouds ofcourse
Now I have 2 x 104hp rack full.
As I have A4, AR and OT, I tried to set a goal for doing stuff with the modular: things which I can´t do with the Elektron machines.
One basic main thing ist the sequencer. I could run the modular from A4 or OT - but that´s not where the modular fun beginnns. Modular Sequencers or trigger based sequencer just can run independly from your straight clock. Think of trig conditions. Let´s say there is a 83% chance the seqencer will go one step further. Not possible with the Elektron gear. But in the modular world there is Pamelas New Workout (which you can sync via DIN SYNC) and little sequencers like Korg SQ1 or Make Noise Rene´. Or you can build your own little sequencer using 2, 3, 3 or more clock divisions and run this into a cv mixer … you know … possibilities are endless.
Soundwise I went with STO and Dixie 2+ for basic great sounding VCOs. (STO has wave shaping). And for chords I went with Braids. I love those wavetables!!!. Also love Clouds parasite firmware in resonator mode. I also added Basimilus Iteritas Alter for drum duties. The key is, to send as many lfos or other moduluations sources as you have into the cv ins. You can send your soundsources to different filters. I went with Z2040 and SSM Filter by Doepfer. Also SEM Filter by Doepfer is good.
Basicly I would say, I was looking for modules that take me in unknown theretories, out of the standard grid workflow, and complement soundwise with the Elektron machines.
But biggest suggestion is: take your time!! You will not learn in a month or two which kind of workflow you like! There a great modules out there but they are a little buggy or a lot of menu diving or what ever. for example I sold Yarns after 2 months because I just was not running as I expected and the menu diving …arrrg! Sometimes you buy a module and use it for 1 or 2 months and it feels great but after that it feels you are done with it and never use it again. It´s a bit tricky with one trick ponies, which most of the modules are.