Hi Peter...
a well worn route is
a sound source, a sound modifier, a modulation source, a way to play and a way to listen...
sound source get something that's a decent size - remember it will need to be tuned - plaits is often seen as a good starter
sound modifier - either a filter or possibly a multi-effect like fx aid xl
modulation source - can't go wrong with maths - see the 'maths illustrated supplement' as a to why - it's a great jumping off point for learning patch-programming (a powerful technique in modular synthesis) and patching in general
a way to play - straight into your mixer - if you get clipping - insert some passive attenuators - they'll always be useful...
a way to play - midi->cv interface if that's what you want...
I'd also add a starter set of utilities - I usually recommend: links, kinks, shades and veils - or modules that cover the same functionality - kinks is discontinued, but there's at least one clone available, happy nerding 3*mia is a good substitute for shades
vcv rack's a great place to start...
have fun!
"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