IMHO, I'd avoid very fancy and fashionable modules. You'll be tempted, maybe, but leave them for later when you figure out your preferred workflow etc. For a somewhat conventional synth/noise machine you'll need:
a) at least two (audio range) oscillators
b) either a filter, or a wavefolder
c) envelopes and/or LFO (or a general-purpose function generator, e.g., Maths, which works as either an EG or a LFO)
d) VCA. Many of them. And you'll need them even if you plan to just make drones. Beginners tend to overlook the importance of VCAs, but they allow you not only to modulate the audio signal, but, most importantly, to modulate the modulators. Having LFOs sweep in and out, etc.
e) mixers. these are not used to mix final signals. Beginners tend to think "I have a proper mixer, no need to include one in the modular". But these are used for instance to mix raw waveforms before a filter or a wavefolder, or to mix two LFOs to get complex oscillations, etc. An outside mixer won't help here.
f) if you have a good collection of pedals and you want to integrate them in your modular setup, a pedal interface. I can't live without my Doepfer A138d.
If I had to start now, I'd go for the cheapest of each I could find. Doepfer if in Europe, Pittsburgh if in the US, I guess.
