how are you playing this? there is no sequencer or midi -> cv module
personally I'd swap out the mixer and the data for an expert sleepers es9 - this will add connectivity to your computer - for vcv rack integration (use a scope in vcv rack) and can be used as a standalone mixer and output... I'd go for a veils clone instead of the curiousers...
I'd also add a couple of simple evelope generatrs, a quad modulation source and a 3rd simple vco (so you can use the fm capabilities of the tzfm osc)
also some form of effect - delay and reverb especially would be a good idea...
on top of those some simple utilities are always going to be useful - something like a happy nerding 3 * mia, a kinks clone, some mults etc
maths is a fantastic module - don't forget to download the 'maths illustrated supplement' and work your way through it multiple times - concentrating on how, what and why it is doing what it is doing - this will massively help with your understanding of patching...
also take a look at my signature... it's a quick guide to getting the most versatility in patching for the least expense...
I would suggest starting with a single voice and the support modules that are needed to get them to work - ie a minimum viable synth - a sound source, a sound modifier, a way to play and a way to listen - possibly plus some of the utilities I mentioned above and learn those modules well before expanding then add a module or 2 once you are happy with your level of understanding and then repeat...
I want it to not waste money on modules that I won’t use
nobody wants to do this, but to a certain extent it is inevitable - you think you want a certain module only to find it's workflow or whatever doen't work for you... luckily there is a decent used market for modules - see marketplace - and often the only cost of tyring a module is the postage...
I think it'd also be a good idea to answer the questions I posed above - as the answers can really help us help you:
what type of music are you trying to make?
what other gear do you have?
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities