When I first got the modular bug the resources that are available now via youtube etc really weren’t there.
In some ways that was good, and in others a source of frustration. I remember it took me maybe an hour to figure out why my first oscillator kept outputting sound continually before realising that “gain” on a VCA wasn’t necessarily what I thought it was - CV controlled the volume, not gain. Ah - that’s what an envelope generator can be used for!
I started with a pretty basic system in terms of synthesis. I experimented a lot and figured things out on my own for quite a long time. As I got more immersed I discovered some internet resources and learned about classics such as Allen Strange’s book. Some of which I then purchased/watched/read and learned more from, or learned the theory behind things I’d already discovered - for example, dynamic depth FM.
I’m glad this is the way I learned modular (although I really don’t think anyone ever has modular “learned” - it’s way to vast). It wasn’t a choice, just how it happened naturally in the circumstances I found myself in at the time. But, starting (relatively) simple and experimenting is the way I’d recommend anyone go about approaching this rabbit hole. Some modules are so complicated and multifaceted these days that not having a grounding in the basics can make them a very difficult experience. I love Buchla’s 259e but if you’d sat me in front of one when I was starting out it would have made little sense to me.
The resources @analogue01 mentions in his post are good ones to give initial experimentation some theoretical grounding.