My understanding is that the more resistance the more gain so there is a minimum of 100 KΩ resistance, then the 1 MΩ pot controls the gain. Then there is a switch for 'Super Crunch' which is a 5 MΩ resistor. Then there are three clipping options: Symmetrical, Asymmetrical (Single-Sided) and Asymmetrical (Double-Sided). Then there is the volume pot, but I don't know what maximum resistance to use. Then at the end is the bypass switch. Would this work? Or am I being dumb. Thanks.
Sorry but this isn't going to work, but well done for having a go. Firstly you have misunderstood "gain". You don't get any gain by putting a 1M pot and a 5M resistor in the signal path, that will just attenuate the signal (make it smaller). To get any gain you need something to provide amplification, such as transistors or an IC called an Operational Amplifier (Op-Amp). Once the Op-Amp has amplified the guitar signal to several volts you can then clip it with diodes - you actually have the right idea with the diodes. I suggest you Google "Guitar Fuzz box schematic", schematics for most of the well know fuzz boxes made over the last 30 years are available.
You might want to start by researching Fuzz Face schematics. It is one of the simpler designs, just make sure you build the NPN version. You don't want to start screwing around with negative 9v power supplies just yet. Start with small easy builds and watch videos of the pedals to find out which sounds resonate with you. Then check out websites for pedal building, many will break down the circuit into their most basic functions. Welcome to the rabbit hole. Breadboarding is a great way to do variations to figure out what each part does. http://diy.smallbearelec.com/HowTos/BreadboardSiFF/BreadboardSiFF.htm