learning to make your own circuits isnt really one of those things that there can be guides for, because it all depends on what kind of circuit you are wanting to make. you basically just have to teach yourself in bits and pieces using the information that is free online. but dont worry, you can learn anything. just start out slow, take your time, and be patient.
do what the other guy said, look at ciruit analysis that break the pedal down into blocks, then learn how to combine the blocks. some of them further break down the blocks into simple circuits and explain them, but some wont they will just say what those simple circuits are. anytime you come across a word or term you dont know, look it up. in the explanation of that there will most likely be other terms you dont know, look those up as well. just keep breaking it down until you get into the raw calculus behind each step of the circuit. dont worry about needing to know calculus and how to solve equations though, just learn how to enter the equations into a free online calculator like wolfram. often times when i am studying electronic theory i will end up with 12 tabs open. it involves a lot of patience and a lot of reading.
electrosmash.com is a good site that has analysis for a lot of common pedals. but also for a lot of simple designs you can just google "(name of pedal) circuit analysis" and something will pop up, and if you dont see anything try googling that but with diystompboxes at the end. that is one of the biggest forums for building pedals. like i said just look up any word or term you dont know. at first your eyes will just kind of glaze over at all the words and math, dont be too intimated by this. just take it one step at a time. the more you get into it, the more it becomes fun and interesting to learn and not so complicated and hard.
also, its easier to start with modding existing designs. that is what i would do first, and you can learn how to do that once you understand what the circuits are doing. i would recommend getting a breadboard and a 20mhz oscilliscope, or learning to how to run a SPICE simulator like LTSPICE. there are also cheaper 10mhz oscilliscopes that are around $50 that would be alright for just starting out, but eventually you will want to upgrade. it really helps you learn if you have some way to visualize the signal. also you really have to be the kind of person that is self-driven, resourceful, and determined. you need to be able to know what the next thing you need to learn is, and what to look up. not saying you arent, but it is a skill and one everyone should practice if they are serious about building unique pedals. also understand that unless you poor every ounce of your being into it, and i mean literally all of your free time and even staying up until 2 am reading about electronic theory, you will not be making crazy awesome high-end boutique-level effects for a few years at least, but even then. it takes a lot of time to get to a point where you can really design something that sticks out in the diy pedal community.
sorry if this is rambly and incoherrent, i am pretty tired and have had a few glasses of wine with thanksgiving dinner lol.