There is no one way to be a goth. There is no “correct” way to be a goth.
Do you like spooky things? Do you have an appreciation for the strange and unusual? Do you look for beauty in dark and unexpected places? Do you like the fashion, the music, the literature, the art? Congratulations, any one of those things means you have goth tendencies, and you can call yourself a goth.
You do not have to be thin.
You do not have to be pale.
You do not have to be over or under a certain age.
You do not have to have a specific hair color, own a certain pair of boots, like a particular band, or have read That One Book.
You are a goth if you say you are.
The only thing you MUST be (IMHO) is accepting of others. Do not be an elitist gatekeeper. And try to be kind.
Goth is as goth does. Don’t ever worry that you aren’t meeting some imaginary checklist. Just be yourself.