You could get into it one part at a time instead of getting everything at once. First, you could be working on how you will create masters from wood, sculpting putty, or whatever you'll use. That's really where the work is. Once you're good at that, get into making the mold tools from the rubber or the clay... however you plan to do the molds. Once you've got your skills up in those two areas, get the resin parts and pour it
There's no need to have mold compounds or resin solutions sitting on the shelf when you've got nothing to cast.
Plain ol' plastic is still important. I like building from rods, strips, tubes & sheets. You don't get to do injection molding with it, so vacuforming and theraforming would be the extended, major area of stock styrene building. The big plus to that is you get to use Tenax, Ambroid or Plastruct weld solvents along with model putties. This could be thought of as being in the area of making masters prior to molding. It's the way to sculpt without clay or wood.
Then there's the finished resin parts which can handle harsh paints without crazing like styrene does. I don't know the limit to what paints resin can handle, but it's pretty high.