What's the way to build a gulp file for custom task

Hi all,
I’m looking for the right way to build custom tasks in a gulpfile
ionic serve
I’ve read this https://coderwall.com/p/5vpvyw/executing-custom-gulp-tasks-when-using-the-ionic-server
which state to add
"gulpStartupTasks": [“browserify”, “sass”, “watch”]
in your ionic.project
I want to build a gulplike like I do in all my web app.

What I’ve done