Learn English – Meaning of “Don’t look down upon your own kind”

Do the needful is Indian English, which has been covered on ELU.

If you're only interacting with other speakers of Indian English then feel free to use it, but avoid it in any other contexts (most Americans and Brits will think it's quaint/uneducated).

In general, the "standard" form is do what[ever] is necessary, but in OP's specific context most likely nothing like that would be used anyway. If you've just asked for an email address, it goes without saying that you want the other person to do whatever is necessary to give you that information.

I may be wrong, but I have the impression that for many Indian English speakers, "Please do the needful" carries a subtext of "This problem is too complex for me to understand or resolve myself, but I have complete faith that you will be able to deal with it, because you are very skilled in such matters"

As I said, Brits and Americans wouldn't normally use any equivalent for such a trivial problem as finding someone's email address. But if the request was for something more challenging (and crucially, if it was from a manager to a more junior worker), "Do what[ever] [you think] is necessary [to solve this problem]" might be perfectly normal. The implication there is that the manager is authorising the junior to do things he might otherwise not be "permitted" to do (in effect, the junior is being temporarily "promoted" for the duration of the problem-solving).

In that context, it should be clear that (to Americans or Brits, at least) any such phrase would probably be considered offensive/cheeky if addressed to an equal in the workplace (if the person asking isn't senior enough to confer temporary authority on you, they shouldn't be speaking to you that way).

I'm a native speaker, and we use "get ready" in exactly the way you describe.

Even though we sometimes qualify the phrase by saying: Get ready for [some event], that "for" clause can be omitted when the listener already knows where we are going. In other words, although get ready can mean different things in different contexts, I can still usually say:

C'mon! We're leaving! You need to get ready!

and that will be understood to mean: put your shoes on, brush your teeth, comb your hair and look presentable, etc.

The precise meaning get ready will vary, depending on where we are going. So long as the hearer knows where we are going, I don't need to add the, say, for your piano practice. For example, I have teenagers at home, so, for me, it works very much like this:

10 or 15 years ago, though, whenever I said, "Let's get ready" to my wife, that always included "Make sure we have the diaper bag!"

You needn't worry about get ready being misconstrued to mean "brace yourself for some bad news" or "get into your starting blocks." Those are very specialized meanings that people wouldn't even think about, unless they were in a situation where that would be the meaning that makes the most sense.

For example, if you wanted your picture taken, and I was holding your camera, I might say, "Get ready..." – which doesn't mean, "go put on your shoes," or, "brace yourself for some bad news." It simply means, "Get ready, I'm going to snap the picture now" – so you should probably just give me your best smile.