Here is my gulpfile that I use to develop my WordPress themes. You can use it as is or modify its configuration to adapt it to your project architecture.
Feel free to suggest improvements by creating issues or fork it !

This project includes lot of nodes module. Please read package.json and package-lock.json to check their own licenses.

1. Install Node.js First, you need to install node.js on your system.
   Visit https://nodejs.org/

2. Clone the repository

3. Install dependencies of npm using npm i

4. Configure browserSync Edit the file gulpfile.js at the root of the projet (lines 14 and 15) to setup the link and the port to use by browserSync like below.

const browserLink = 'http://localhost/'
const browserPort = 3030

5. You're done
   Work in the /_src folder, all your changes will automatically be optimized and copied to the right place using the npx gulp command during development or npx gulp build to build your project.

I prefer to use package locally so I use npx to execute gulp. If you prefer to call gulp directly, install it globally : npm i -g gulp

When developing, use browser sync to speed up your productivity. It'll compile the scss, prefixes it, quickly optimize images, minify scripts and copy PHP files to the good folder.

Optimize your project before upload it ! It'll compile the scss, prefixes it, better optimize images (with an acceptable lossy compression), minify scripts and copy PHP files to the good folder.

For any reason you what to clean-up the project by delete build files. It will clear caching and delete all build files to just keep essential files and sources.

I prefer to use package locally so I use npx to execute gulp. If you prefer to call gulp directly, install it globally : npm i -g gulp