first I would get a bigger case (6u/104hp is a good sized starter case) so you can actually build a modular synth in it rather than a collection of a few modules that won't play nicely together

you need to add modulation, envelope generators, utility modules

either a bigger case or cut back to 1 or 2 voices at most - otherwise not enough space for the support modules you need

"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