Lugia has solid advice. I started off first with an Elektron Analog 4 and Make Noise 0-coast semi-modular several years ago. Fast forward from 2016 to 2020 today. I downloaded VCV Rack and ordered the book Patch & Tweak and really learned a lot. Then this summer I bought a Doepfer A100 Basic System 1 with room for adding more modules to learn modular in rack and that helped me to further understand how VCOs, VCAs, VCF and envelopes and LFO modulation work together as well as the need for support modules like attenuators, mults and logic modules. This month I ordered a much larger case and more modules. Still learning but quite a journey. One thing to keep in mind: always always get a much larger case! I recommend at least something like a Doepfer 9u powered suitcase or perhaps an MDLR 12u case. These are still portable but have lot of room for the many support modules you will need versus just a bunch of the cool oscillator modules.