I would do some more research first - specifically reading a load of other newbie with semi wanting to get into modular posts - here and muffwiggler are both good starting points
as farkas pointed out there is no point racking the semi-s
if you already have the semis - then it maybe an idea to concentrate this rack on modulation/utilities/effects/mixing
the first modules I would get would be links, kinks, shades, a quad cascading vca, a filter (non-moog inspired), maths and something that can do delay and/or reverb (FX Aid XL perhaps)
and nothing else - play with that until you know it back to front and expand slowly and organically from there based upon your own experience
at the very minimum download the maths illustrated manual and work your way through the patches in it a good few times with the modules you do have - probably one of the best learning techniques for modular there is!
use the output of the vca as a final output stage for now - most will drive headphones or speakers - output modules are a weird topic - those who have them swear by them and those that don't generally say - they are superfluous, unless you absolutely need balanced outs (which you probably don't)
"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