Hello dear, 

For JEE Mains, the eligibility is: 

• The candidates who are born on or after october 1,1993 are eligible to apply for Jee main 2019 exam. 
• Candidates who have passed in 12th in 2017 and 2018 are eligible to give exam in 2019
• The candidates appearing in class 12th in 2019 are also eligible. 

Therefore, you can give exam after one year gap or you can give it immediately, its your wish.

All the best!