I just can't set up a local testing environment for SCSS on Mac

I've looked at a few guides and have tried to install a workflow with git, and tried another with just terminal commands (gulp sass). I cannot figure out how to set up a testing environment for SCSS and I'm really tired of writing it blind. I can't get it to compile, even when I run the SCSS through sassmeister and it has no errors.

Does anyone have recommendations for a comprehensive guide for how to set up an SCSS + HTML testing environment? I have found a couple online, but they're from 2010 and 2011, and most of them seem to be for Windows.

I just need to be able to see the style changes in the HTML when I'm writing the SCSS and test it in browser.