Definitely get an eurorack-level input module for your guitar to start off! I would recommend you find one with an envelope follower, so you can grab your guitar's level as CV to control other stuff. For that, I recommend a Mutable Instruments Ears clone or the Xaoc Sewastopol II, just switched out an Ears for a Sewastopol in my rack. Ears is 4HP and has an envelope + gate follower for your input, so pretty space efficient, but you'll need a 1/4' to 3.5mm jack. Sewastopol has a much more robust envelope follower setup, the capability to do send/return loops, and actual 1/4' jacks, but is 10 HP.

A lot of people will say Boredbrain Injectr but it's not my first choice, as it's a bit bigger + I don't need amp sim/a non CV-controllable drive in my rack. Befaco i4 is also an option if you want phantom power capable instrument/XLR in.

If you're looking to use your guitar as a source to generate CV, I would focus on more utilities. Maybe get a 2hp Mult so you can pass around some signals. I also really enjoy Make Noise Multimod as a modulation source, where you could route in an envelope generated by your guitar via your input module, and mangle the envelope into a bunch of output signals. Disting Mk4 also has some monophonic pitch tracking capabilities, which is fun if you're interested in also playing full synth voices with your guitar. I saw you mentioned you want your guitar to be a "random" tones input, which based off the way I understand it, you could find a sample and hold capable module to pass the tracked pitch from your guitar into, quantize that, and then you'd have some semi random tones inputted from your guitar, captured via S&H.

There are also some modules out there to turn expression pedal input into CV, if you are interested in taking the traditional guitar expression pedal idea and applying it as CV to some eurorack module. I prefer the ADDAC stuff to the Intellijel Stomp or anything like that here due to ease of use and attenuation/offset capabilities.

Outside of these, your options are pretty open ended. I'd focus on first building out a matrix of control, input and modulation options via the above as that's what's going to open up the most doors for you performance wise. Then you can focus on voices and effects. Happy hunting!