The idea behind a procedural generation system is that you input a bit of data, and it spits back a more complex dataset that was 'grown' in a logical manner according to defined rules.

A simplified programming challenge to think about for this would be something like "From a starting point, draw a random line, between a defined min and max length, at a min/max angle offset from the previous line (if any), and stop if the point falls outside of a boundary box."

However I feel that starting from a procedural generation stand point for a city is a very awkward and difficult way to go about building a game world. Starting with a procedurally generated terrain to begin building your city is a good starting point. You would then start adding 'key points' and roads connecting things. Once you have a 'core frame work', then a procedural 'in fill' function to add in all the extra things can be extremely valuable.

You shouldn't be spending time placing street lights, signs, or fire hydrants ideally, but rather build a system to populate those things for you.

where do i input the data? i'm confused

It sounds to me like you're in the early planning stages and you don't really need a procedurally generated city. Maybe just start simple by drawing out a city map on paper or a paint program so you can get a bit of an idea of what you want in the way of important buildings, character's homes, geographical characteristics, where things appear in relation to each other, and maybe a general street plan. When you have everything that you need planned in general, then you can start asking about what the best way might be to create a 3D representation of your map.

It sounds to me like you're in the early planning stages and you don't really need a procedurally generated city. Maybe just start simple by drawing out a city map on paper or a paint program so you can get a bit of an idea of what you want in the way of important buildings, character's homes, geographical characteristics, where things appear in relation to each other, and maybe a general street plan. When you have everything that you need planned in general, then you can start asking about what the best way might be to create a 3D representation of your map.

the game is in rpg maker vx ace so it's 2d and tile based

Oh, very sorry for the confusion there. I didn't realize you were building this based on a tool like that.

This is the kind of thing that is typically done by way of custom software that is tailored to the project. I'm not familiar with the specific tool you're using, or the map file specification, but working toward building a "Map editor" version of your game is frequently a very handy part of a project development cycle.

However this may be a sub-project that will require you to step back from your main goals to lean and address things, and is generally not a trivial thing to do.

Your solution to the problem may end up looking like something along the lines of:

- Use the tools in RPG Maker to establish an initial 'proto-map'

- Export the map files and load into a custom tool

- Generate additional details according to rules and conditions you write

- Move map into the game (Or continue refining the map with editing tools you make yourself.)

- Test that your map works for your desired game play.

I'm sorry that I'm not more familiar with the tools and able to offer more direct help. Good luck with your project.

The maps what i'm doing at the moment is using paint.net and combining realistic textures with pixel art which seems to look alright at the moment, just having issues putting everything together into neighborhoods and boroughs, I'm thinking if i design the crime organizations first i could base areas around them but i'm also trying to think how a city would look if say i combined new york, detroit, new orleans, LA and vegas but not sure how it'd look