This has nothing to do with Optimizely CMS, imo.

If you are using Google Analytics I would use action trigger as Chris is mentioning; add a click event to the button (inline, or general button event in javascript). 

for example; 

ga('send','event','Click','Button click','Button/block name');

Since the tracker already know the page (hopefully) you can use the button name which could be returned from the block, in the view.

Throwing in my 50p's worth here.

I agree with Jonas in that this is not Optimizely CMS related and more a Google Tracking issue.

The way I like to do this however is slightly different.

Most sites I have worked with use Google Tag Manager (GTM) to implement Google Analytics (GA).

GTM has more capabilities and allow you to add other javascript functionality to the site for example chat clients, cookie managers, ODP, etc, without need for some developer support.

In order to use GTM for tracking you must then be able to provide GTM with some data, this can be achieve by using data attributes in the markup. Here we are keeping the customised javascript outside the solution and the page will not need to load an additional script on load.

In GTM you can then set up tags to fire when buttons / links are clicked, they will retrieve the data from the data attributes and then pass this to GA.

You can read more about this approach here.

I like this approach as the markup will be standardised and specific for GTM, this way a developer will not interfer with tracking.

Paul

Thanks a lot for valuable information