What I tend to recommend folk do in the synth-diy community is to find existing designs like Yves Usson's yusynth stuff, and make a "cover version" of it. Draw the circuit diagram, and from that draw the PCB, trying to keep them as close as possible to the originals.

That way you're climbing the "using the tools" learning curve separately from the "laying out designs" learning curve, which makes it all a lot easier.