can you apply for study visa with 1 year gap in studies?

YES! Most countries abroad allow a study gap of one year for a master's degree. However, to explain this gap you can give genuine reasons for this gap in your letter of explanation. You can explain about what you were doing while working, acquired some special technical skills, or acquired proficiency in using certain computer software/programs, etc.   

One of the most important sets of documents required for a visa interview is the academic documents. Academic documents required for a study visa include: 

Test Scores: Have both the GRE and TOEFL/IELTS test scores with you. If the original test scores have not yet arrived, you can always download a copy of your results off the internet from your ETS account.
Degree Certificate: If you have graduated, you should have your degree certificate with you. If you are yet to graduate make sure to have at least all your 8-semester grade sheets with you. If not, at least your course completion certificate.
Mark Sheets for all semesters, TC and Immigration Certificate (if available)
Academic Transcripts
10th and 12th Mark Sheets 
 

I hope this was helpful. Let me know if you have any more questions.