I want to track button clicks, which lead to external website. I want to put them in Google Analytics Goals.
Is there any option to this without Google Tag Manager?
Rather than write a bunch of extra code, you can follow this guide. Pretty simple. Your link text could be (most likely will be) different throughout your entire website. GTM will simply track every single click and report on it.
http://mediacause.org/track-button-clicks-google-tag-manager/