You're wanting to build up a system around a Moog Grandmother. All well and good...but to do what, exactly? Don't ask what modules are the ones you should have based on generalizations like that, because the methods for a build is created should always take the MUSICAL requirements in mind FIRST. For example, if you want to direct your musical efforts more toward something rhythmic and danceable, that gamut of modules isn't going to be the same as what you'd need if you were doing industrial/noise, or ambient, or sound design work, or...well, you get the idea.
Creating a modular system for your specific needs is not a simple process. If done correctly, it's not on the order of simplicity of going to the grocery and getting ingredients for a recipe. It requires you to really understand what your music is now, and where you want to go with it in the long-term as long as you want to avoid a pointless outlay of piles of cash on modules that you find aren't ones that work for your purposes. Plus, how well do you know that Moog? That's not been out that long...so have you fully explored its own potential to a suitable limit where you really understand what functions it has that you want to expand upon?
Those are things you need to start on before starting in on slapping together hardware...even in a virtual form such as on MG. Spend some time in things such as VCV Rack (a modular emulator...very useful for exploring module functions and combinations). Spend time on here alongside that, looking into which modules are for what best purpose, alone and in combinations with other modules. Spend time looking at important 'historical' instruments, and find out why they were assembled with the module/circuit complements they have. And expect this to TAKE time; I know people are enamored with instant gratification these days, and ample Magic Plastic + synth retailers galore might seem to make that possible, but the plain fact is that rushing into that situation without ample preparation is a recipe for massive annoyance and fiscal ugliness...and certainly NOT any sort of gratification, unless you're a masochist.