Here's a list of the gear OP mentioned:
Intellijel Rubicon2
Joranalogue filter8
Intellijel quadvca
Xaoc batumi
Make noise maths
Intellijel dual adsr
Hexinverter mutant brain
Disting EX

I have all of those modules except the Hexinverter and Disting EX. They are very tasty indeed.

Some considerations when you get your NEXT round of funding:

  1. Buy the Poti expander for the Batumi. It gives you front panel access to a lot more features and is worth it (3HP)
  2. Buy a second VCO (doesn't have to be a Rubicon) for stacking voices, adding subs, audio-rate effects, sync, etc.
  3. A noise module would go well. They are often paired with sample & hold circuits... which is also useful.
  4. A small DC-coupled mixer module. The Maths can mix... but a dedicated 3:1 or 4:1 mixer will free up the Maths for better functions.
  5. A simple sequencer that has at least a clock and reset input. 8 or 16 steps should be fine. Think of something under $200. Sequencers are for more than just playing notes. You might also like something like an Ornaments & Crime (micro) that can handle simple sequencing duties, or quantizing, etc.

I can think of a lot more modules to have fun with. But those would be high up on my list.