ok planning on taking the semis out of the case in the future - you get a pass on this
maths can work well in all racks...
I wouldn't worry about filling the case all at once - personally I think a single voice - vco, filter, modulation source (possibly maths) & a decent vca (quad cascading) plus a way to play & a way to listen is a good start, then add a few utilities and then think about more voices is a better way to go
"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