DIYers these days are both blessed and cursed with access to hundreds if not thousands of amazing and well-documented pedal projects, where all you have to do is buy the PCB and put it together. This makes it incredibly easy to build a functional pedal, even a reasonably complex one, on your first try.
The downside is that it's become increasingly easy to build pedals without understanding how pedals work. You can become a skilled assembler with no knowledge of what's going on in the circuit, building loads of pedals without even reading a schematic. There's nothing inherently wrong with this if building pedals is your end goal, but if you want to understand enough to design your own pedals, you're going to need to reach past available projects.
My first piece of advice if you haven't already, learn to read a schematic. You need to know what the components are and what they look like, acknowledging that there can be variations based on software and whoever drew them. Once you've done that, the next step would be to devour all the schematics you can get your hands on. This does the same thing for you that reading books does in learning a language: you'll start to recognize patterns, see common ways to do things, and when odd things do present themselves you'll recognize them as being odd so you can look them up and figure out what's going on. Granted this isn't as easy as grabbing a dictionary, but the aforementioned Ohm's and Kirchoff's laws are a great starting point for general circuit analysis and will never stop being pertinent.
Once you've consumed enough schematics to start recognizing patterns and common circuit blocks, a logical next step would be to combine some blocks into something you might like. Maybe you're a big fan of the Rat but want to try a different tone control, maybe you want a Tubescreamer with a boost on the front end. Take building blocks of circuits you've seen and smash them together into something else. Compare your schematic with schematics you've seen that have common building blocks and compare how you implemented it with how it was done before.
Once you have a schematic that makes some sense, take it to the breadboard. Now breadboarding can be considered a skill all its own, as there are tips and tricks that make the process more convenient, but with your schematic as a guide you should be able to put some things together and make some noise. One benefit to breadboarding is that you're not constrained to using the input or output as drawn in the schematic, you can try just putting together one piece at a time to hear how that piece sounds, then add blocks in until you like the sound. It's important though that any changes you make during breadboarding also make their way back to your schematic so you can revise it to match the circuit you actually built.
Once you have a breadboarded design that's been verified, the next reasonable step would be to swing a PCB design, but the details of that are way out of scope for this already-too-long reply.
As you continue to do mashups of other circuits you'll start to understand more of how things work in the abstract, and at that point you can stop saying "I want this to sound like a Muff" and start saying "I think cascading another NPN stage here would give me the saturation I'm looking for." And at that point, my dude, the world is your oyster. That's when the hobby starts to get reeeaaalllly expensive.
Hopefully something in there is useful, I like talking about pedal stuff and I get carried away sometimes
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