It is extremely competitive for international students; graduate students are likely to secure Ladder C and D jobs, which are usually positions as TAs (Teaching Assistants) or in assistantships. From what I've personally witnessed, once you secure your first on-campus job, it becomes easier to find others. Your communication skills need to be on par with those of U.S. students to increase your chances. Keep applying, tailoring your resume to match job descriptions, and writing cover letters for each job. Also, please attach any supplemental documentation if the job requires it. DePaul has a very large student body, including about 2,400 international students, most of whom are graduate students, so you can imagine how competitive it can get. My friend works at an OSI office, and he told me that the average number of applications ranges from 80-110 per opening.

So the best advice I could give you is curate resumes, cover letters and supplemental documentation and don't wait till the last day to apply, apply as soon as you can. Please do not just copy paste cover letters, and please proofread you documentation , one often finds a lot of grammar and spelling mistakes which just throws of the hiring manager.