Mobile applications sharing mechanism know who shared to who

I'm currently developing an android application. In the future(I hope so) iOS + Web will also be developed.

In my application i need to make a sharing mechanism. What i want to do with is to allow users to share posts on Facebook and any social network.

When a some user (Not the one who shared from the app) I want to make him go to the Google Play(Android) / My Website(Web)/ App Store(iOS) and make him download it or open it if he installed it already.

Afterwards once the user signs up , I wanna know which user(the one that shared my app) message that was post on the social network was used to make the user(new user to my app that downloaded it or using it for the first time) to register my app.

Basically all I wanna do is to build or use some mechanism that lets me know who shared the app and who entered my app and signed up because of the user that shared the app.

Note - I dont wanna be platform depended on Facebook or any social network. I want to come up with a solution that works for all cases.

I saw some posts online that tells people to use Google Analytics. It seems like a good tool, but I wanted to receive some reviews about it before i use it and maybe get a tip or two for making this mechanism.

Thanks :)