CIBIL is basically to track defaulters. However, you should have sufficient Income Proof. Lets say at least Rs 20,000 / Month before you can apply for a Credit Card. Best income is from salary and the creditor will verify your presence in the office as well.
Now, don't go on applying for credit cards as this will make it obvious you are hungry for credit and everybody will deny. Wait for a year before you re-apply until then work on earning more.
Since Citi has rejected your Card Application, you have the right to your CIBIL Report by paying not more than Rs 50. Search Cardbhai.com and I have a detailed post on how to procure the same. Get it and keep it with you for your future reference.