Here's a fairly complicated patch on my analogue systems modular..just to show you how messy it can get. But you just take one thing at a time, and add onto it. Nothing can ever be broken by inserting cables. Just have the "out to in, out to in" philosophy while you're making the sound. If there is no sound the audio chain is broken somewhere, look over it again, check if some output lvl is set to zero etc.
Download the moog modular V demo from arturia, then you get a good look at the factory sounds it comes with..
Usually everything is out to in, for instance a saw out to mixer in, mixer out to filter input, filter out to vca in, vca out to speaker.
But some modulations like envelope generators and LFO's are patched in from "outside the chain", then you patch the LFO/EG out to whatever you want to modulate, like oscillator pitch or filter cutoff's input.
The huge module on top is a step sequencer. On top of that is an effects unit. The one with bright green light in a MIDI/CV converter with lcd panel.
My system has 3 oscillators, 2 filters, 2 mixers, ring modulator, LFO, 2 EG's, VCA, a step sequencer and some other useful control modules.