if you can't decide if you have enough or need more of something the simple and probably best answer is to postpone that decision until you can actually make it
buy a one or a couple of extra modules now and then work out what you need from playing with it
it's even easier if you buy the disting now - set it up as the modules you may think you want - it has vcas and quite a few different utilities, alng with quite a few other things - all of which are 'decent' or better fr what they are - and have a play, get used to using those algos (use favourites to simplify the module) and if you find yourself using disting as a vca then get a vca, or whatever
particularly if this happens for vcas - get more channels - a triple or quad cascading vca for example
if you think you need a mixer early on again get the cascading vca - its a vc-mixer!!! and it's vcas
the other great modules I have that work like this are maths and stages - they do what they do on the surface and then you can program them to do many many other things - i don't know about a stages illustrated manual, but the maths illustrated manual is a phenomenal learning tool - read it even if you don't have a maths or want a maths - you may need one afterwards
"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