The meaning of ください as a verb is "Give me(something)". We use "verbて+ください" as "Please do(verb)" in English. お願いします is a polite form of 願います means "I pray/wish". We use お願いします as "Please" in English. So you have to say ~てください first. And you can add お願いします to it, if you want to express your keen desire or politeness. ~てください has a concrete meaning. But お願いします doesn't.
どうか一度会ってください。(お願いします。)Please meet me once.(Please!)
And you can use お願いします as a reply to a proposal.
こちらから電話しましょうか。Shall I call you? ええ、お願いします。Yes, please.
You can also use ええ、そうしてください。Yes, do it, please.