One of the best things I've heard someone say about this is that being an ally is a verb, not a noun. It's not a static state. It's about what you DO.

I have read that one of the Best depictions of an ally is Martin Freeman's character in Black Panther. He does no make it about himself. He does not want cookies. He does not go mighty whitey on you. He shuts up when the Wakandans are talking and asks "how can I help?"