First of all, the best starting strategy immediately proceeds from the understanding that MODULAR IS EXPENSIVE. That's not even rule #1...it's more like a basic law of physics. A primary setup is going to cost a significant amount of money...period. Even going with the less expensive makers is going to cost a chunk, since they don't make everything you'll need and since you'll want a sturdy and properly-powered case to stuff everything in.
Also, instead of feeling butthurt about Ronin's advice above, I'd suggest going back and reading it again. It might BE a "default answer"...but that's because you're already falling into default traps. Points #1 and #2 are actually extremely important and not merely flip replies. That advice is 100% spot-on and you ignore/deprecate it at your own peril. Or peril to your credit rating, because you'll wind up spending a lot to get very little in return.
Lastly, if the focus here is sound design, you might consider two other options:
1) Get a vintage modular/patchable. Something like an ARP 2600 is expensive, true, but you'll wind up learning a lot more out of something that had researched design principles behind it, plus an undeniable sound quality. And if not that, a more recent patchable based on older paradigms (such as a Buchla Sound Easel, or Kilpatrick's Phenol, which is based on Serge concepts) would make just as much sense and probably be easier to maintain.
2) Consider whether you actually need a modular synth in the first place. Frankly...and this might sound heretical on MG...you may find more use in a large, modern polysynth like a Moog One or Waldorf Quantum as far as sound design is concerned than you'd get out of a modular system that's built without proper research, funding, and system discipline. Or stay in software; have you explored the possibilities of something such as Iris2, PPG Ultimate, etc in tandem with a good library of other processing plugins?
In either of the above cases, you'll potentially wind up spending pretty much the same amount of money as a properly-scaled modular system. But they're more likely to yield an immediate result. Modular isn't about immediate results; it's more of a long-term process between the user and the instrument, and if you want those immediate results, you'd probably be better off not frustrating yourself with modular.