module unavailability is just something you get used to - it's worse thanks too covid, but it's still not unusual to have to wait for the module you want
Buy the important modules that you want
Work out what modules you need to support them and go from there
Might be an idea to post a starting rack to see if anything is missing
and remember there's nothing wrong with substituting module A with module B if you can't find module A and module B will do most (or all) of what module A does - either as a stop gap or permanently
there are no wrong paths in your modular journey - some are just more expensive than others
"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