To me, being a "bitcoiner" means having full faith in Bitcoin over fiat currencies and altcoins. However, the definition may vary depending on how each person sees Bitcoin. I don't have a lot of Bitcoin, only hundreds of thousands of satoshis, but even so, I believe in Bitcoin.
Of course, for you to be able a full-pledged bitcoiner, you have to develop complete trust into bitcoin and keep it as a priority towards altcoins and meme coins. You are making a good promotion about it, not in a sense of spreading good information about bitcoin online, but using it in a positive purpose that will make the people realized that bitcoin is for our own good welfare, and it shouldn’t be an instrument towards negative purposes.
Also, being a good bitcoiner means you have better access on it whether as an investment or as a currency, and that fiat is only a back up knowing its value will only depreciate in the long run.