(I second the YT suggestion. I’m partial to Modular Curiosity personally, in spite of it mostly being a relic of the v1 days.)
In response to your particular questions, the unsatisfying-but-honest answer is It Depends. Nevertheless, I can recommend a few favorites.
Oscillators–it depends, based on what kind of sound palette you want to start from. Grandiose, detuned sounds? Try a supersaw-alike such as Flag Prodigal Son or Synth Tech Cloud Generator. Pure sounds? Go for something like Bogaudio FM-OP or Vult Basal, or just pull any old sinusoid osc out of a hat. An overall massive sound? Try something like Vult Vessek or Noxious.
That being said, don’t sleep on docB Pad/Pad 2 which are implementations of the Padsynth algorithm which is particularly good at generating glassy ‘clusters’ of harmonically related partials; Valley Terrorform, which, although it’s quite complex, is one of those things that does everything and does it well, combining wavetables, waveshapers, a suboscillator, a lowpass gate, etc.; and the Audible Instruments Resonator, which, despite not being a traditional oscillator, can be either ‘pinged’ or used as a processor for a huge range of rich, naturalistic sounds.
Also, noise is your friend. The standard VCV noise generator is excellent, and for any patch where that leaves something to be desired, Befaco Noise Plethora more than lives up to its name.
Modulation–the more the merrier, and do pile on the LFOs, envelopes, and modulation sequencers for sure, for which you can take your pick. But moreover I really love function generators, which may combine any or all of the above, plus a wealth of other logical functions, triggers, slew limiting, etc. In my library, Befaco Rampage reigns supreme, and I also like the Audible Segment Generator (although I can’t claim to have fully wrapped my head around that one in terms of effectively using it to its utmost). Fun exercise: try building a patch using function generators for virtually everything–oscillators, envelopes, LFOs, filters, and so on.
Otherwise, I’m really into using chaotic signal generators, which are great for producing cyclic modulation (or even semi-pitched audio sources that occasionally burst into crazy noise), either individual signals or multiple interrelated ones, without quite repeating themselves. I’m especially a fan of Vult Caudal and the chaos generators in Magus Instrumentalis’ “Madness” set, but I heartily recommend HetrickCV’s as well, which has tons of interesting chaos modules.
Honorable mention: VCV Random is butt-kicking random/noise/sample & hold module.
Reverb–plenty of good reverbs in the VCV library, but for my money, Valley Plateau totally rules.
For delay, I usually reach for Alright Devices’ Chronoblob 2, which sounds great, is clockable, modulable, has a few different modes, and will take a mono or stereo signal. It’s super clean though, so if I do want something with a little more “sauce”, I usually like a BBD model like Lindenberg Sangster or Flag Tap Dancer.
For ambient music, I usually find myself layering contrasting textures from monophonic signals, but polyphony can be a lot of fun as well. One technique I use a lot is using polyphonic merge & split to mux/demux a bunch of sequences or modulation sources to, say, an oscillator or filter or something, which unifies the control set, saves a lot of screen real estate, and usually saves a bit of CPU overhead over using multiple individual modules per each signal.
Hope that all provides you some food for thought at least…
