Custom Exceptions, how much is too much?

I've been wondering how many exceptions should I have, I've seen other posts saying that it is good to have multiple exceptions it improves readability of your code and better understanding of the error if there is one.

Now I have 5 exceptions, check UserNotFoundException and AccountExpenseNotFoundException basically both exceptions are the same, but referring to different entities.

Is this a bad practice?
Should I make an exception like EntityNotFound to handle this?

No, this is good. The one downside is that you end up writing something like:

try {
   bookkeeperthingie();
} catch (AccountExpenseAlreadyExistsException |
   AccountExpenseNotFoundException | UsernameOrPasswordInvalidException |
   Blablabla | Morebla e) {
}

to avoid that, make sure your exceptions follow a hierarchy. You might for example have:

public class BookkeepingException extends Exception {
    public BookkeepingException(String msg) { super(msg); }
    public BookkeepingException(String msg, Throwable cause) { super(msg, cause); }
}

public class AccountExpenseAlreadyExistsException extends BookkeepingException { ... }

and so forth. If you find it particularly plausible that a user of your API would want to catch any kind of 'bookkeeping thingie not found' exception, make that a level in the hierarchy (but that that doesn't sound right to me).

Now you could write:

try {
    bookkeepingthingie();
} catch (BookkeepingException e) {
}

if you don't particularly care about the kind of thing that went wrong, and catch a more specific one if you do, or even combine them (if not found, do this. for any other bookkeeping issue, do this - you can do that with a hierarchy; catch the more specific one first, then the general one).