Hi! I'm an international student too, and I'm about to start my graduate study this fall. Here's a little something about myself. I hope it can help you gain some confidence when you apply. I'm straight out of undergrad and my only work experience was a one month full-time internship in a local government's foreign affairs office. I had some international volunteer experience, but none of them was longer than a month. (VISA restriction sucks) Well as you can see, you definitely have a stronger background in working than I do. Since I managed to get in some schools that I really like, I believe you will too in the near future.
I think when applying, the most important thing is to show the ad comm how you fit their program. Sure work experience in related field is of great significance, but you can still show that you're a good fit by emphasizing your other strengths, your unique experience and your motivation in your personal statement.
I hope this will help.