I’ve lost a lot of my knowledge being here, but I’ll try to help you!
I typically drink my tea plain, or sometimes with a little sugar. Some people prefer honey over sugar. I’m not really sure why - maybe it melts easier into the tea. I don’t usually mess with honey because it’s sticky and has the potential to make a mess.
As for milk, I only put it in Indian teas like chai. Other people like it more often. I think it’s all personal taste. There’s not really a right or wrong way to tea. Still, I think milk is really only used with dark teas. In China, though, there’s never any sugar or milk for tea! Not that we saw, anyway.