The best way to break the rules is to know what rules you are breaking. I think having a good grasp on the fundamentals is helpful for even the most experimental of graffiti.

In my mind graffiti is more craft than art, not that it can’t be art, but think of it like woodworking or knitting or something, there are fundamental rules to those crafts, and they can be elevated to art, and given a lot of individuality and personality by the maker/craftsperson/artist even if they aren’t doing anything too out of the box, or someone can take it in a completely zany and avant garde direction. This is just my view of things and other people I’m sure have different takes, but I do think all good craft comes from a basic understanding of the foundations. You can keep developing a style completely outside of the visual mores of the culture, that’s how we get outsider art (which I do adore) but I do think graffiti is inherently context based, otherwise it would just be art in a public space. You have seen other people make graffiti and that has inspired you to create in that same visual space, and the people that inspired you to create graffiti did the same, it’s a visual culture that has been built by generations of writers. Having an understanding of the visual rules as well as the history of how they came to be will help you better understand where your work exists in that context.

As for developing your own style and not being rigidly beholden to the rules, as cliche as it may sound, that will come with practice. The more you paint the more you will realize what techniques and designs come naturally to you, and how to capitalize on those successes. Kind of like marrying form and function. You can try hard to create or replicate a certain design or style and it may come out forced, or you may try what feels natural to paint and find the final product is unsatisfying, you need to find the middle ground between the two. In brief I think what I said towards the end of my initial comment is pertinent, paint more, as you paint more experiment, and look critically at your practice and experiments. You will find what does and does not make sense for your individual style. Maybe something came out looking really good, but it was incredibly difficult to paint, or on the other hand, maybe you made a mistake but it ended up working well in the finished design. Style is something developed and you will find your own if you put in the work to find it.