I would start with breadboards and modules from SparkFun or Adafruit. You can mock up a lot of functionality without needing to solder anything. If you get to the point where you're ready to jump into PCB design, check out the /r/printedcircuitboard wiki: https://www.reddit.com/r/PrintedCircuitBoard/wiki/index/. You might be able to find similar projects that have been posted and critiqued there already. SparkFun and Adafruit both publish their schematics/PCB layouts. I recommend KiCad for your PCB/schematic software - there are plenty of KiCad tutorials and guides on Youtube. Have fun!