In case my opinion may be useful, six months ago I started with modular hardware. I have started with a very tight budget, and acquiring modules for a "basic" patch (VCO, filter, VCA's, basic Envelopes).
After many "patch and unpatch" I think that, although the basic utilities (VCA's, LFO's, envelopes) are essential, but more complex modules are the ones that give more room for experimentation. Mainly effects (delay, distortion), waveshapers and filters with some extra function.
I think that now I have entered a second phase, where I am exploring for example my Endorphin.es Airstreamer and my NE Viol Ruina filter and although they are quite basic modules, it is surprising what they give of themselves.