It's certainly better to put it on your application than to leave a blank if you don't have ptehr work experience.
Even if it's not a completely unique graduate experience or directly relevant to the job, at least it shows you did something constructive with that time.
As you mention, you learned a lot from the experience, and setting out what you learned is a great way to leverage it into your application. Focus on any specific competencies or skills that the company has set out in the job description.
That said, there's no need to go overboard making out that every holiday job was a fundamentally life-changing epiphany.
Your interviewer will have a reasonable idea what teaching english abroad, bar work, volunteering at a soup kitchen, involves. Seeing something like this on a graduate application, along with some intelligent analysis of what the applicant did and learned, I would think "fair enough, they did something with their time". When people go OTT about how their year spent travelling is a perfect analogy for a consulting project I'm more likely to think "either they're an idiot to assume I'm that gullible, or they're an idiot to actually believe this tripe".