No problem. It is a bit of minefield to start with; so much to take in!
I started with pedals which are a lot easier in terms of inventory/BOM requirements (they typically use a lot of the same components and values).
For Diode’s and IC’s (Opamps, voltage regulators etc.) the BOM/schematic should state what value. If not then that is not a very clear schematic.
For through hole capacitors you are typically looking at 2.5mm or 5mm spacing.
Traditionally film capacitors were used in audio signal paths, but Multi Layer Ceramic Capacitors (MLCC’s) are being used more and more and should do the job fine (don’t tell the audiophiles though!).
As a very general rule for capacitors (for use in audio applications) from what I have learned:
Below 1nF = Typically use a ceramic capacitor (typically 2.5mm spacing).
1nF-1uF = Typically use a film capacitor (typically 5mm spacing).
Above 1uF = Typically use an electrolytic capacitor (spacing dependent on voltage rating).
Be careful with voltage ratings for capacitors (especially electrolytics). As a very general rule go for a voltage rating near enough double that of your supply voltage.
E.g. I would go for 25V rated Electrolytic caps for Eurorack projects.
If you are in the UK, Rapid Online (https://www.rapidonline.com/) is a lot easier to navigate and find standard parts than Farnell. Thonk is a very good resource for pots and the more obscure stuff.
I would also look at the Music Thing project. Many are through hole, and are very well documented and have clear schematics, BOM’s etc.
Hope this helps!