How to implement a rating system in the game?

Question

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Good afternoon!
I almost finished my project, but I want to add a rating so that users can see how many other players have scored via the Internet, how can I implement this if I don’t have my own server and don’t want to pay anyone for it?
In addition to mobile devices, the project is planned to be uploaded to vk, it would be interesting to implement a rating system for this social network separately, so that users can see how many points their friends have scored. Can I somehow implement this?
Thanks for the replies
ADDITION:
Project on Unity3D
The rating is based on the number of player's points (who has more points, the higher)

Answer 1

you feel sorry for 100r per month? you can leave on average 600 rubles in one McDonald's at a time, or ride a minibus ~ 4 times.
vds.menu to help you.
it is not clear from the task how you and what you are doing the game on. how the rating system should be formed.

Answer 2

parse.com has a free plan to get you started . And the magic word for Google is BAAS (backend-as-a-service).

Answer 3

For example, at first, many people use this: parse.com (free with low load)
You can also take free hosting for these tasks: beget.ru/free-hosting