English isn't a language where you can omit words down to a single word sentence in everyday conversations. For a complete sentence, you almost always need a subject and a verb. So with the examples you provided, "I need help," the I is necessary. When asking another directly, "Need help?" is acceptable. Off of the top of my head, commands are an example where things do end up getting cut to one word. "Some help" and "help" are relatively the same. "Some" just modifies "help" specifying the amount of help.