initial thoughts:

2 sound sources is 1 too many for this size rack, imo

steppy is a trigger sequencer - which is great if you want to trigger percussion etc, however not great for sequencing melodies, admittedly you could use the scales as I believe that has a small v/oct sequencer in it - but - pams will do random quantized sequences that you can loop and do most of the trigger sequencing that steppy would provide

so I would initially at least drop one of the sound sources and both steppy and scales

if you are planning on using this with other instruments how are you connecting them? keeping them in sync etc? would a midi or dc-coupled audio interface make sense?

advice:
a rough guide to building a decent modular in terms of ratio of modules:

sound sources < sound modifiers < modulation sources < utilities (including anything else like sequencers, output modules, vcas, mixers, switches, logic)

it scales from tiny cases right up to 1000s of hp

why? because a single sound source can be copied and processed differently, a few simple modulation sources can be mixed and modified to become more modulation sources that are more complex

Personally I don't think that this rack is good from the point of learning modular synthesis

a good starting point for learning modular synthesis is a sound source (anything - a cheap used analog vco will do, as will plaits), a sound modifier (a low pass filter - if you want to spend more get a multi effect like fx aid too), a modulation source (I like maths as a starter modulation source - see below), a way to listen (I always suggest a quad cascading vca like veils 1st, but you have the outs) and a way to play it (pams will do fine but is a bit of a pita to program and I can't see the screen in certain lighting conditions) - really useful additions are a utility starter set (mults, unity mixers, basic logic sample and hold, a dc-coupled vca)

why maths? google the maths illustratted supplement - it is a guide to self-patching maths in 32 different ways to get it to do differnt things other than it's most basic and obvious functions - working your way through this multiple times is a fantastic primer for modular synthesis - as all the principles/thought processes learnt will transfer to bigger systems - other modules can be sustituted, but they don't have the same level of

why veils? better bet than the mixer/vca you have - it has more channels, it is dc-coupled so you can use it for cv as well as audio (which is a fundamental technique of modular synthesis) it can be split so that you can use a couple of channels as a vc mixer and still use other channels for other things, it has enough gain to be used as an input module for external instruments if needed

what starter utilities? I usually recommend links, kinks, shades and veils - but kinks is now discontinued - if you can find one buy it! wmd/ssf toolbox is a very capable replacment as it has a lot of the same functions plus a few more - the modules themselves are not important - it is what they do so substituting other modules that cover the same ground is a great idea - just do you research - read manuals etc etc

btw I wouldn't recommend stages as a first modulation source - it's great but complicated and a lot of people find it a bit confusing to use for anything other than simple envelopes despite it's myriad of other functions - including sample and hold - simpler single mode modules are probably better to start with

NB sample and hold is not random - you need to feed it a noise source or random cv signal or any other signal to get anything out of it

"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