When's the right time?

So how quickly is it ok to ask a girl to dinner, just on a casual, i want to get to know you date? After a few small talk convos? After hanging out with friends? What's the norm here

Your question is pretty vague but it really depends on how well you get along, if two people have a real connection then don't wait.

I think 5 minutes into a good conversation is long enough. That's how long it would take me to decide whether or not I was interested in meeting you again.