Expressing yourself publicly in what way? Do you mean visually through fashion, verbally, or?
I've learned just to force myself to do whatever I need to do and sometimes to make myself feel most comfortable I dress to match my current feelings more so than to match the location I am going to or will be in.
What you wear can depend on its social acceptability depending on the situation just like what you say can be limited by the context you are communicating in. But my opinion is that it makes more sense to feel comfortable with yourself before you expect others to feel comfortable with you. You can't control how people react to what you wear or what you say. You can be polite about it and can follow social rules based on expectations of acceptableness but I feel like a lot of what we worry about is stuff that most people don't even notice and even if they do their minds are onto the next topic of interest as soon as their eyes or ears see or hear something else.
Practice is important. You can practice what you say, how you say it, what you wear, how you wear it etcetera but you need to practice feeling comfortable first because feeling safe is the most important part.